diff --git a/pre_commit/clientlib.py b/pre_commit/clientlib.py
index d742ef4b..46ab3cd0 100644
--- a/pre_commit/clientlib.py
+++ b/pre_commit/clientlib.py
@@ -1,7 +1,7 @@
 import argparse
 import functools
 import logging
-import pipes
+import shlex
 import sys
 from typing import Any
 from typing import Dict
@@ -25,18 +25,17 @@ check_string_regex = cfgv.check_and(cfgv.check_string, cfgv.check_regex)
 def check_type_tag(tag: str) -> None:
     if tag not in ALL_TAGS:
         raise cfgv.ValidationError(
-            'Type tag {!r} is not recognized.  '
-            'Try upgrading identify and pre-commit?'.format(tag),
+            f'Type tag {tag!r} is not recognized.  '
+            f'Try upgrading identify and pre-commit?',
         )
 
 
 def check_min_version(version: str) -> None:
     if parse_version(version) > parse_version(C.VERSION):
         raise cfgv.ValidationError(
-            'pre-commit version {} is required but version {} is installed.  '
-            'Perhaps run `pip install --upgrade pre-commit`.'.format(
-                version, C.VERSION,
-            ),
+            f'pre-commit version {version} is required but version '
+            f'{C.VERSION} is installed.  '
+            f'Perhaps run `pip install --upgrade pre-commit`.',
         )
 
 
@@ -142,9 +141,7 @@ def _entry(modname: str) -> str:
     runner, so to prevent issues with spaces and backslashes (on Windows)
     it must be quoted here.
     """
-    return '{} -m pre_commit.meta_hooks.{}'.format(
-        pipes.quote(sys.executable), modname,
-    )
+    return f'{shlex.quote(sys.executable)} -m pre_commit.meta_hooks.{modname}'
 
 
 def warn_unknown_keys_root(
@@ -152,9 +149,7 @@ def warn_unknown_keys_root(
         orig_keys: Sequence[str],
         dct: Dict[str, str],
 ) -> None:
-    logger.warning(
-        'Unexpected key(s) present at root: {}'.format(', '.join(extra)),
-    )
+    logger.warning(f'Unexpected key(s) present at root: {", ".join(extra)}')
 
 
 def warn_unknown_keys_repo(
@@ -163,9 +158,7 @@ def warn_unknown_keys_repo(
         dct: Dict[str, str],
 ) -> None:
     logger.warning(
-        'Unexpected key(s) present on {}: {}'.format(
-            dct['repo'], ', '.join(extra),
-        ),
+        f'Unexpected key(s) present on {dct["repo"]}: {", ".join(extra)}',
     )
 
 
diff --git a/pre_commit/commands/autoupdate.py b/pre_commit/commands/autoupdate.py
index 2e5ecdf9..fd98118a 100644
--- a/pre_commit/commands/autoupdate.py
+++ b/pre_commit/commands/autoupdate.py
@@ -80,13 +80,12 @@ def _check_hooks_still_exist_at_rev(
     hooks_missing = hooks - {hook['id'] for hook in manifest}
     if hooks_missing:
         raise RepositoryCannotBeUpdatedError(
-            'Cannot update because the tip of master is missing these hooks:\n'
-            '{}'.format(', '.join(sorted(hooks_missing))),
+            f'Cannot update because the tip of HEAD is missing these hooks:\n'
+            f'{", ".join(sorted(hooks_missing))}',
         )
 
 
 REV_LINE_RE = re.compile(r'^(\s+)rev:(\s*)([^\s#]+)(.*)(\r?\n)$', re.DOTALL)
-REV_LINE_FMT = '{}rev:{}{}{}{}'
 
 
 def _original_lines(
@@ -122,13 +121,11 @@ def _write_new_config(path: str, rev_infos: List[Optional[RevInfo]]) -> None:
         new_rev = new_rev_s.split(':', 1)[1].strip()
         if rev_info.frozen is not None:
             comment = f'  # frozen: {rev_info.frozen}'
-        elif match.group(4).strip().startswith('# frozen:'):
+        elif match[4].strip().startswith('# frozen:'):
             comment = ''
         else:
-            comment = match.group(4)
-        lines[idx] = REV_LINE_FMT.format(
-            match.group(1), match.group(2), new_rev, comment, match.group(5),
-        )
+            comment = match[4]
+        lines[idx] = f'{match[1]}rev:{match[2]}{new_rev}{comment}{match[5]}'
 
     with open(path, 'w') as f:
         f.write(''.join(lines))
diff --git a/pre_commit/commands/install_uninstall.py b/pre_commit/commands/install_uninstall.py
index f0e56988..7aeba228 100644
--- a/pre_commit/commands/install_uninstall.py
+++ b/pre_commit/commands/install_uninstall.py
@@ -14,7 +14,6 @@ from pre_commit.repository import all_hooks
 from pre_commit.repository import install_hook_envs
 from pre_commit.store import Store
 from pre_commit.util import make_executable
-from pre_commit.util import mkdirp
 from pre_commit.util import resource_text
 
 
@@ -78,7 +77,7 @@ def _install_hook_script(
 ) -> None:
     hook_path, legacy_path = _hook_paths(hook_type, git_dir=git_dir)
 
-    mkdirp(os.path.dirname(hook_path))
+    os.makedirs(os.path.dirname(hook_path), exist_ok=True)
 
     # If we have an existing hook, move it to pre-commit.legacy
     if os.path.lexists(hook_path) and not is_our_script(hook_path):
@@ -89,8 +88,8 @@ def _install_hook_script(
         os.remove(legacy_path)
     elif os.path.exists(legacy_path):
         output.write_line(
-            'Running in migration mode with existing hooks at {}\n'
-            'Use -f to use only pre-commit.'.format(legacy_path),
+            f'Running in migration mode with existing hooks at {legacy_path}\n'
+            f'Use -f to use only pre-commit.',
         )
 
     params = {
@@ -110,7 +109,7 @@ def _install_hook_script(
         hook_file.write(before + TEMPLATE_START)
         for line in to_template.splitlines():
             var = line.split()[0]
-            hook_file.write('{} = {!r}\n'.format(var, params[var]))
+            hook_file.write(f'{var} = {params[var]!r}\n')
         hook_file.write(TEMPLATE_END + after)
     make_executable(hook_path)
 
diff --git a/pre_commit/commands/run.py b/pre_commit/commands/run.py
index c5da7e3c..2cf213a7 100644
--- a/pre_commit/commands/run.py
+++ b/pre_commit/commands/run.py
@@ -1,4 +1,5 @@
 import argparse
+import contextlib
 import functools
 import logging
 import os
@@ -27,7 +28,6 @@ from pre_commit.staged_files_only import staged_files_only
 from pre_commit.store import Store
 from pre_commit.util import cmd_output_b
 from pre_commit.util import EnvironT
-from pre_commit.util import noop_context
 
 
 logger = logging.getLogger('pre_commit')
@@ -173,7 +173,7 @@ def _run_single_hook(
 
         if out.strip():
             output.write_line()
-            output.write_line(out.strip(), logfile_name=hook.log_file)
+            output.write_line_b(out.strip(), logfile_name=hook.log_file)
             output.write_line()
 
     return files_modified or bool(retcode)
@@ -243,9 +243,10 @@ def _run_hooks(
         output.write_line('All changes made by hooks:')
         # args.color is a boolean.
         # See user_color function in color.py
+        git_color_opt = 'always' if args.color else 'never'
         subprocess.call((
             'git', '--no-pager', 'diff', '--no-ext-diff',
-            '--color={}'.format({True: 'always', False: 'never'}[args.color]),
+            f'--color={git_color_opt}',
         ))
 
     return retval
@@ -271,7 +272,7 @@ def run(
         args: argparse.Namespace,
         environ: EnvironT = os.environ,
 ) -> int:
-    no_stash = args.all_files or bool(args.files)
+    stash = not args.all_files and not args.files
 
     # Check if we have unresolved merge conflict files and fail fast.
     if _has_unmerged_paths():
@@ -280,10 +281,10 @@ def run(
     if bool(args.source) != bool(args.origin):
         logger.error('Specify both --origin and --source.')
         return 1
-    if _has_unstaged_config(config_file) and not no_stash:
+    if stash and _has_unstaged_config(config_file):
         logger.error(
-            'Your pre-commit configuration is unstaged.\n'
-            '`git add {}` to fix this.'.format(config_file),
+            f'Your pre-commit configuration is unstaged.\n'
+            f'`git add {config_file}` to fix this.',
         )
         return 1
 
@@ -292,12 +293,10 @@ def run(
         environ['PRE_COMMIT_ORIGIN'] = args.origin
         environ['PRE_COMMIT_SOURCE'] = args.source
 
-    if no_stash:
-        ctx = noop_context()
-    else:
-        ctx = staged_files_only(store.directory)
+    with contextlib.ExitStack() as exit_stack:
+        if stash:
+            exit_stack.enter_context(staged_files_only(store.directory))
 
-    with ctx:
         config = load_config(config_file)
         hooks = [
             hook
@@ -308,12 +307,13 @@ def run(
 
         if args.hook and not hooks:
             output.write_line(
-                'No hook with id `{}` in stage `{}`'.format(
-                    args.hook, args.hook_stage,
-                ),
+                f'No hook with id `{args.hook}` in stage `{args.hook_stage}`',
             )
             return 1
 
         install_hook_envs(hooks, store)
 
         return _run_hooks(config, hooks, args, environ)
+
+    # https://github.com/python/mypy/issues/7726
+    raise AssertionError('unreachable')
diff --git a/pre_commit/commands/try_repo.py b/pre_commit/commands/try_repo.py
index 767d2d06..5e7c667d 100644
--- a/pre_commit/commands/try_repo.py
+++ b/pre_commit/commands/try_repo.py
@@ -1,5 +1,4 @@
 import argparse
-import collections
 import logging
 import os.path
 from typing import Tuple
@@ -62,8 +61,7 @@ def try_repo(args: argparse.Namespace) -> int:
             manifest = sorted(manifest, key=lambda hook: hook['id'])
             hooks = [{'id': hook['id']} for hook in manifest]
 
-        items = (('repo', repo), ('rev', ref), ('hooks', hooks))
-        config = {'repos': [collections.OrderedDict(items)]}
+        config = {'repos': [{'repo': repo, 'rev': ref, 'hooks': hooks}]}
         config_s = ordered_dump(config, **C.YAML_DUMP_KWARGS)
 
         config_filename = os.path.join(tempdir, C.CONFIG_FILE)
diff --git a/pre_commit/error_handler.py b/pre_commit/error_handler.py
index 6e67a890..77b35698 100644
--- a/pre_commit/error_handler.py
+++ b/pre_commit/error_handler.py
@@ -3,10 +3,9 @@ import os.path
 import sys
 import traceback
 from typing import Generator
-from typing import Union
+from typing import Optional
 
 import pre_commit.constants as C
-from pre_commit import five
 from pre_commit import output
 from pre_commit.store import Store
 
@@ -15,25 +14,24 @@ class FatalError(RuntimeError):
     pass
 
 
-def _to_bytes(exc: BaseException) -> bytes:
-    return str(exc).encode('UTF-8')
-
-
 def _log_and_exit(msg: str, exc: BaseException, formatted: str) -> None:
     error_msg = b''.join((
-        five.to_bytes(msg), b': ',
-        five.to_bytes(type(exc).__name__), b': ',
-        _to_bytes(exc),
+        msg.encode(), b': ',
+        type(exc).__name__.encode(), b': ',
+        str(exc).encode(),
     ))
-    output.write_line(error_msg)
+    output.write_line_b(error_msg)
     store = Store()
     log_path = os.path.join(store.directory, 'pre-commit.log')
     output.write_line(f'Check the log at {log_path}')
 
     with open(log_path, 'wb') as log:
-        def _log_line(s: Union[None, str, bytes] = None) -> None:
+        def _log_line(s: Optional[str] = None) -> None:
             output.write_line(s, stream=log)
 
+        def _log_line_b(s: Optional[bytes] = None) -> None:
+            output.write_line_b(s, stream=log)
+
         _log_line('### version information')
         _log_line()
         _log_line('```')
@@ -50,7 +48,7 @@ def _log_and_exit(msg: str, exc: BaseException, formatted: str) -> None:
         _log_line('### error information')
         _log_line()
         _log_line('```')
-        _log_line(error_msg)
+        _log_line_b(error_msg)
         _log_line('```')
         _log_line()
         _log_line('```')
diff --git a/pre_commit/five.py b/pre_commit/five.py
deleted file mode 100644
index df59d63b..00000000
--- a/pre_commit/five.py
+++ /dev/null
@@ -1,12 +0,0 @@
-from typing import Union
-
-
-def to_text(s: Union[str, bytes]) -> str:
-    return s if isinstance(s, str) else s.decode('UTF-8')
-
-
-def to_bytes(s: Union[str, bytes]) -> bytes:
-    return s if isinstance(s, bytes) else s.encode('UTF-8')
-
-
-n = to_text
diff --git a/pre_commit/git.py b/pre_commit/git.py
index 07be3350..fd8563f1 100644
--- a/pre_commit/git.py
+++ b/pre_commit/git.py
@@ -69,7 +69,7 @@ def is_in_merge_conflict() -> bool:
 def parse_merge_msg_for_conflicts(merge_msg: bytes) -> List[str]:
     # Conflicted files start with tabs
     return [
-        line.lstrip(b'#').strip().decode('UTF-8')
+        line.lstrip(b'#').strip().decode()
         for line in merge_msg.splitlines()
         # '#\t' for git 2.4.1
         if line.startswith((b'\t', b'#\t'))
@@ -183,13 +183,11 @@ def check_for_cygwin_mismatch() -> None:
         if is_cygwin_python ^ is_cygwin_git:
             exe_type = {True: '(cygwin)', False: '(windows)'}
             logger.warn(
-                'pre-commit has detected a mix of cygwin python / git\n'
-                'This combination is not supported, it is likely you will '
-                'receive an error later in the program.\n'
-                'Make sure to use cygwin git+python while using cygwin\n'
-                'These can be installed through the cygwin installer.\n'
-                ' - python {}\n'
-                ' - git {}\n'.format(
-                    exe_type[is_cygwin_python], exe_type[is_cygwin_git],
-                ),
+                f'pre-commit has detected a mix of cygwin python / git\n'
+                f'This combination is not supported, it is likely you will '
+                f'receive an error later in the program.\n'
+                f'Make sure to use cygwin git+python while using cygwin\n'
+                f'These can be installed through the cygwin installer.\n'
+                f' - python {exe_type[is_cygwin_python]}\n'
+                f' - git {exe_type[is_cygwin_git]}\n',
             )
diff --git a/pre_commit/languages/docker.py b/pre_commit/languages/docker.py
index 4bef3391..00090f11 100644
--- a/pre_commit/languages/docker.py
+++ b/pre_commit/languages/docker.py
@@ -81,7 +81,7 @@ def install_environment(
 
 def get_docker_user() -> str:  # pragma: windows no cover
     try:
-        return '{}:{}'.format(os.getuid(), os.getgid())
+        return f'{os.getuid()}:{os.getgid()}'
     except AttributeError:
         return '1000:1000'
 
@@ -94,7 +94,7 @@ def docker_cmd() -> Tuple[str, ...]:  # pragma: windows no cover
         # https://docs.docker.com/engine/reference/commandline/run/#mount-volumes-from-container-volumes-from
         # The `Z` option tells Docker to label the content with a private
         # unshared label. Only the current container can use a private volume.
-        '-v', '{}:/src:rw,Z'.format(os.getcwd()),
+        '-v', f'{os.getcwd()}:/src:rw,Z',
         '--workdir', '/src',
     )
 
diff --git a/pre_commit/languages/fail.py b/pre_commit/languages/fail.py
index 1ded0713..ff495c74 100644
--- a/pre_commit/languages/fail.py
+++ b/pre_commit/languages/fail.py
@@ -18,6 +18,6 @@ def run_hook(
         file_args: Sequence[str],
         color: bool,
 ) -> Tuple[int, bytes]:
-    out = hook.entry.encode('UTF-8') + b'\n\n'
-    out += b'\n'.join(f.encode('UTF-8') for f in file_args) + b'\n'
+    out = hook.entry.encode() + b'\n\n'
+    out += b'\n'.join(f.encode() for f in file_args) + b'\n'
     return 1, out
diff --git a/pre_commit/languages/helpers.py b/pre_commit/languages/helpers.py
index b39f57aa..3a9d4d6d 100644
--- a/pre_commit/languages/helpers.py
+++ b/pre_commit/languages/helpers.py
@@ -51,8 +51,8 @@ def assert_no_additional_deps(
 ) -> None:
     if additional_deps:
         raise AssertionError(
-            'For now, pre-commit does not support '
-            'additional_dependencies for {}'.format(lang),
+            f'For now, pre-commit does not support '
+            f'additional_dependencies for {lang}',
         )
 
 
diff --git a/pre_commit/languages/node.py b/pre_commit/languages/node.py
index cb73c12a..914d8797 100644
--- a/pre_commit/languages/node.py
+++ b/pre_commit/languages/node.py
@@ -30,10 +30,10 @@ def _envdir(prefix: Prefix, version: str) -> str:
     return prefix.path(directory)
 
 
-def get_env_patch(venv: str) -> PatchesT:  # pragma: windows no cover
+def get_env_patch(venv: str) -> PatchesT:
     if sys.platform == 'cygwin':  # pragma: no cover
         _, win_venv, _ = cmd_output('cygpath', '-w', venv)
-        install_prefix = r'{}\bin'.format(win_venv.strip())
+        install_prefix = fr'{win_venv.strip()}\bin'
         lib_dir = 'lib'
     elif sys.platform == 'win32':  # pragma: no cover
         install_prefix = bin_dir(venv)
@@ -54,14 +54,14 @@ def get_env_patch(venv: str) -> PatchesT:  # pragma: windows no cover
 def in_env(
         prefix: Prefix,
         language_version: str,
-) -> Generator[None, None, None]:  # pragma: windows no cover
+) -> Generator[None, None, None]:
     with envcontext(get_env_patch(_envdir(prefix, language_version))):
         yield
 
 
 def install_environment(
         prefix: Prefix, version: str, additional_dependencies: Sequence[str],
-) -> None:  # pragma: windows no cover
+) -> None:
     additional_dependencies = tuple(additional_dependencies)
     assert prefix.exists('package.json')
     envdir = _envdir(prefix, version)
@@ -91,6 +91,6 @@ def run_hook(
         hook: 'Hook',
         file_args: Sequence[str],
         color: bool,
-) -> Tuple[int, bytes]:  # pragma: windows no cover
+) -> Tuple[int, bytes]:
     with in_env(hook.prefix, hook.language_version):
         return helpers.run_xargs(hook, hook.cmd, file_args, color=color)
diff --git a/pre_commit/languages/pygrep.py b/pre_commit/languages/pygrep.py
index 6b8463d3..c6d1131d 100644
--- a/pre_commit/languages/pygrep.py
+++ b/pre_commit/languages/pygrep.py
@@ -27,7 +27,7 @@ def _process_filename_by_line(pattern: Pattern[bytes], filename: str) -> int:
             if pattern.search(line):
                 retv = 1
                 output.write(f'{filename}:{line_no}:')
-                output.write_line(line.rstrip(b'\r\n'))
+                output.write_line_b(line.rstrip(b'\r\n'))
     return retv
 
 
@@ -39,12 +39,12 @@ def _process_filename_at_once(pattern: Pattern[bytes], filename: str) -> int:
         if match:
             retv = 1
             line_no = contents[:match.start()].count(b'\n')
-            output.write('{}:{}:'.format(filename, line_no + 1))
+            output.write(f'{filename}:{line_no + 1}:')
 
-            matched_lines = match.group().split(b'\n')
+            matched_lines = match[0].split(b'\n')
             matched_lines[0] = contents.split(b'\n')[line_no]
 
-            output.write_line(b'\n'.join(matched_lines))
+            output.write_line_b(b'\n'.join(matched_lines))
     return retv
 
 
diff --git a/pre_commit/languages/python.py b/pre_commit/languages/python.py
index 3fad9b9b..b9078113 100644
--- a/pre_commit/languages/python.py
+++ b/pre_commit/languages/python.py
@@ -47,10 +47,10 @@ def _find_by_py_launcher(
         version: str,
 ) -> Optional[str]:  # pragma: no cover (windows only)
     if version.startswith('python'):
+        num = version[len('python'):]
         try:
             return cmd_output(
-                'py', '-{}'.format(version[len('python'):]),
-                '-c', 'import sys; print(sys.executable)',
+                'py', f'-{num}', '-c', 'import sys; print(sys.executable)',
             )[1].strip()
         except CalledProcessError:
             pass
@@ -88,7 +88,7 @@ def get_default_version() -> str:  # pragma: no cover (platform dependent)
         return exe
 
     # Next try the `pythonX.X` executable
-    exe = 'python{}.{}'.format(*sys.version_info)
+    exe = f'python{sys.version_info[0]}.{sys.version_info[1]}'
     if find_executable(exe):
         return exe
 
@@ -96,7 +96,8 @@ def get_default_version() -> str:  # pragma: no cover (platform dependent)
         return exe
 
     # Give a best-effort try for windows
-    if os.path.exists(r'C:\{}\python.exe'.format(exe.replace('.', ''))):
+    default_folder_name = exe.replace('.', '')
+    if os.path.exists(fr'C:\{default_folder_name}\python.exe'):
         return exe
 
     # We tried!
@@ -135,7 +136,8 @@ def norm_version(version: str) -> str:
         # If it is in the form pythonx.x search in the default
         # place on windows
         if version.startswith('python'):
-            return r'C:\{}\python.exe'.format(version.replace('.', ''))
+            default_folder_name = version.replace('.', '')
+            return fr'C:\{default_folder_name}\python.exe'
 
     # Otherwise assume it is a path
     return os.path.expanduser(version)
diff --git a/pre_commit/languages/ruby.py b/pre_commit/languages/ruby.py
index 9f98bea7..fb3ba931 100644
--- a/pre_commit/languages/ruby.py
+++ b/pre_commit/languages/ruby.py
@@ -79,29 +79,6 @@ def _install_rbenv(
         _extract_resource('ruby-download.tar.gz', plugins_dir)
         _extract_resource('ruby-build.tar.gz', plugins_dir)
 
-    activate_path = prefix.path(directory, 'bin', 'activate')
-    with open(activate_path, 'w') as activate_file:
-        # This is similar to how you would install rbenv to your home directory
-        # However we do a couple things to make the executables exposed and
-        # configure it to work in our directory.
-        # We also modify the PS1 variable for manual debugging sake.
-        activate_file.write(
-            '#!/usr/bin/env bash\n'
-            "export RBENV_ROOT='{directory}'\n"
-            'export PATH="$RBENV_ROOT/bin:$PATH"\n'
-            'eval "$(rbenv init -)"\n'
-            'export PS1="(rbenv)$PS1"\n'
-            # This lets us install gems in an isolated and repeatable
-            # directory
-            "export GEM_HOME='{directory}/gems'\n"
-            'export PATH="$GEM_HOME/bin:$PATH"\n'
-            '\n'.format(directory=prefix.path(directory)),
-        )
-
-        # If we aren't using the system ruby, add a version here
-        if version != C.DEFAULT:
-            activate_file.write(f'export RBENV_VERSION="{version}"\n')
-
 
 def _install_ruby(
         prefix: Prefix,
diff --git a/pre_commit/logging_handler.py b/pre_commit/logging_handler.py
index 807b1177..ba05295d 100644
--- a/pre_commit/logging_handler.py
+++ b/pre_commit/logging_handler.py
@@ -21,16 +21,12 @@ class LoggingHandler(logging.Handler):
         self.use_color = use_color
 
     def emit(self, record: logging.LogRecord) -> None:
-        output.write_line(
-            '{} {}'.format(
-                color.format_color(
-                    f'[{record.levelname}]',
-                    LOG_LEVEL_COLORS[record.levelname],
-                    self.use_color,
-                ),
-                record.getMessage(),
-            ),
+        level_msg = color.format_color(
+            f'[{record.levelname}]',
+            LOG_LEVEL_COLORS[record.levelname],
+            self.use_color,
         )
+        output.write_line(f'{level_msg} {record.getMessage()}')
 
 
 @contextlib.contextmanager
diff --git a/pre_commit/main.py b/pre_commit/main.py
index ce902c07..eae4f909 100644
--- a/pre_commit/main.py
+++ b/pre_commit/main.py
@@ -9,7 +9,6 @@ from typing import Union
 
 import pre_commit.constants as C
 from pre_commit import color
-from pre_commit import five
 from pre_commit import git
 from pre_commit.commands.autoupdate import autoupdate
 from pre_commit.commands.clean import clean
@@ -155,7 +154,6 @@ def _adjust_args_and_chdir(args: argparse.Namespace) -> None:
 
 def main(argv: Optional[Sequence[str]] = None) -> int:
     argv = argv if argv is not None else sys.argv[1:]
-    argv = [five.to_text(arg) for arg in argv]
     parser = argparse.ArgumentParser(prog='pre-commit')
 
     # https://stackoverflow.com/a/8521644/812183
diff --git a/pre_commit/meta_hooks/check_useless_excludes.py b/pre_commit/meta_hooks/check_useless_excludes.py
index 1359e020..30b8d810 100644
--- a/pre_commit/meta_hooks/check_useless_excludes.py
+++ b/pre_commit/meta_hooks/check_useless_excludes.py
@@ -34,8 +34,7 @@ def check_useless_excludes(config_file: str) -> int:
     exclude = config['exclude']
     if not exclude_matches_any(classifier.filenames, '', exclude):
         print(
-            'The global exclude pattern {!r} does not match any files'
-            .format(exclude),
+            f'The global exclude pattern {exclude!r} does not match any files',
         )
         retv = 1
 
@@ -50,8 +49,8 @@ def check_useless_excludes(config_file: str) -> int:
             include, exclude = hook['files'], hook['exclude']
             if not exclude_matches_any(names, include, exclude):
                 print(
-                    'The exclude pattern {!r} for {} does not match any files'
-                    .format(exclude, hook['id']),
+                    f'The exclude pattern {exclude!r} for {hook["id"]} does '
+                    f'not match any files',
                 )
                 retv = 1
 
diff --git a/pre_commit/output.py b/pre_commit/output.py
index 88857ff1..b20b8ab4 100644
--- a/pre_commit/output.py
+++ b/pre_commit/output.py
@@ -1,11 +1,10 @@
 import contextlib
 import sys
+from typing import Any
 from typing import IO
 from typing import Optional
-from typing import Union
 
 from pre_commit import color
-from pre_commit import five
 
 
 def get_hook_message(
@@ -54,21 +53,18 @@ def get_hook_message(
         assert end_msg is not None
         assert end_color is not None
         assert use_color is not None
-        return '{}{}{}{}\n'.format(
-            start,
-            '.' * (cols - len(start) - len(postfix) - len(end_msg) - 1),
-            postfix,
-            color.format_color(end_msg, end_color, use_color),
-        )
+        dots = '.' * (cols - len(start) - len(postfix) - len(end_msg) - 1)
+        end = color.format_color(end_msg, end_color, use_color)
+        return f'{start}{dots}{postfix}{end}\n'
 
 
 def write(s: str, stream: IO[bytes] = sys.stdout.buffer) -> None:
-    stream.write(five.to_bytes(s))
+    stream.write(s.encode())
     stream.flush()
 
 
-def write_line(
-        s: Union[None, str, bytes] = None,
+def write_line_b(
+        s: Optional[bytes] = None,
         stream: IO[bytes] = sys.stdout.buffer,
         logfile_name: Optional[str] = None,
 ) -> None:
@@ -80,6 +76,10 @@ def write_line(
 
         for output_stream in output_streams:
             if s is not None:
-                output_stream.write(five.to_bytes(s))
+                output_stream.write(s)
             output_stream.write(b'\n')
             output_stream.flush()
+
+
+def write_line(s: Optional[str] = None, **kwargs: Any) -> None:
+    write_line_b(s.encode() if s is not None else s, **kwargs)
diff --git a/pre_commit/parse_shebang.py b/pre_commit/parse_shebang.py
index cab90d01..c1264da9 100644
--- a/pre_commit/parse_shebang.py
+++ b/pre_commit/parse_shebang.py
@@ -9,7 +9,7 @@ from identify.identify import parse_shebang_from_file
 
 class ExecutableNotFoundError(OSError):
     def to_output(self) -> Tuple[int, bytes, None]:
-        return (1, self.args[0].encode('UTF-8'), None)
+        return (1, self.args[0].encode(), None)
 
 
 def parse_filename(filename: str) -> Tuple[str, ...]:
diff --git a/pre_commit/repository.py b/pre_commit/repository.py
index 83ed7027..9b071089 100644
--- a/pre_commit/repository.py
+++ b/pre_commit/repository.py
@@ -12,7 +12,6 @@ from typing import Set
 from typing import Tuple
 
 import pre_commit.constants as C
-from pre_commit import five
 from pre_commit.clientlib import load_manifest
 from pre_commit.clientlib import LOCAL
 from pre_commit.clientlib import MANIFEST_HOOK_DICT
@@ -49,7 +48,7 @@ def _write_state(prefix: Prefix, venv: str, state: object) -> None:
     state_filename = _state_filename(prefix, venv)
     staging = state_filename + 'staging'
     with open(staging, 'w') as state_file:
-        state_file.write(five.to_text(json.dumps(state)))
+        state_file.write(json.dumps(state))
     # Move the file into place atomically to indicate we've installed
     os.rename(staging, state_filename)
 
@@ -137,8 +136,8 @@ class Hook(NamedTuple):
         extra_keys = set(dct) - set(_KEYS)
         if extra_keys:
             logger.warning(
-                'Unexpected key(s) present on {} => {}: '
-                '{}'.format(src, dct['id'], ', '.join(sorted(extra_keys))),
+                f'Unexpected key(s) present on {src} => {dct["id"]}: '
+                f'{", ".join(sorted(extra_keys))}',
             )
         return cls(src=src, prefix=prefix, **{k: dct[k] for k in _KEYS})
 
@@ -154,11 +153,9 @@ def _hook(
     version = ret['minimum_pre_commit_version']
     if parse_version(version) > parse_version(C.VERSION):
         logger.error(
-            'The hook `{}` requires pre-commit version {} but version {} '
-            'is installed.  '
-            'Perhaps run `pip install --upgrade pre-commit`.'.format(
-                ret['id'], version, C.VERSION,
-            ),
+            f'The hook `{ret["id"]}` requires pre-commit version {version} '
+            f'but version {C.VERSION} is installed.  '
+            f'Perhaps run `pip install --upgrade pre-commit`.',
         )
         exit(1)
 
@@ -210,10 +207,9 @@ def _cloned_repository_hooks(
     for hook in repo_config['hooks']:
         if hook['id'] not in by_id:
             logger.error(
-                '`{}` is not present in repository {}.  '
-                'Typo? Perhaps it is introduced in a newer version?  '
-                'Often `pre-commit autoupdate` fixes this.'
-                .format(hook['id'], repo),
+                f'`{hook["id"]}` is not present in repository {repo}.  '
+                f'Typo? Perhaps it is introduced in a newer version?  '
+                f'Often `pre-commit autoupdate` fixes this.',
             )
             exit(1)
 
diff --git a/pre_commit/resources/hook-tmpl b/pre_commit/resources/hook-tmpl
index 9bf2af7d..213d16ee 100755
--- a/pre_commit/resources/hook-tmpl
+++ b/pre_commit/resources/hook-tmpl
@@ -39,7 +39,7 @@ def _norm_exe(exe: str) -> Tuple[str, ...]:
         if f.read(2) != b'#!':
             return ()
         try:
-            first_line = f.readline().decode('UTF-8')
+            first_line = f.readline().decode()
         except UnicodeDecodeError:
             return ()
 
@@ -52,12 +52,11 @@ def _norm_exe(exe: str) -> Tuple[str, ...]:
 def _run_legacy() -> Tuple[int, bytes]:
     if __file__.endswith('.legacy'):
         raise SystemExit(
-            "bug: pre-commit's script is installed in migration mode\n"
-            'run `pre-commit install -f --hook-type {}` to fix this\n\n'
-            'Please report this bug at '
-            'https://github.com/pre-commit/pre-commit/issues'.format(
-                HOOK_TYPE,
-            ),
+            f"bug: pre-commit's script is installed in migration mode\n"
+            f'run `pre-commit install -f --hook-type {HOOK_TYPE}` to fix '
+            f'this\n\n'
+            f'Please report this bug at '
+            f'https://github.com/pre-commit/pre-commit/issues',
         )
 
     if HOOK_TYPE == 'pre-push':
@@ -77,25 +76,22 @@ def _run_legacy() -> Tuple[int, bytes]:
 
 def _validate_config() -> None:
     cmd = ('git', 'rev-parse', '--show-toplevel')
-    top_level = subprocess.check_output(cmd).decode('UTF-8').strip()
+    top_level = subprocess.check_output(cmd).decode().strip()
     cfg = os.path.join(top_level, CONFIG)
     if os.path.isfile(cfg):
         pass
     elif SKIP_ON_MISSING_CONFIG or os.getenv('PRE_COMMIT_ALLOW_NO_CONFIG'):
-        print(
-            '`{}` config file not found. '
-            'Skipping `pre-commit`.'.format(CONFIG),
-        )
+        print(f'`{CONFIG}` config file not found. Skipping `pre-commit`.')
         raise EarlyExit()
     else:
         raise FatalError(
-            'No {} file was found\n'
-            '- To temporarily silence this, run '
-            '`PRE_COMMIT_ALLOW_NO_CONFIG=1 git ...`\n'
-            '- To permanently silence this, install pre-commit with the '
-            '--allow-missing-config option\n'
-            '- To uninstall pre-commit run '
-            '`pre-commit uninstall`'.format(CONFIG),
+            f'No {CONFIG} file was found\n'
+            f'- To temporarily silence this, run '
+            f'`PRE_COMMIT_ALLOW_NO_CONFIG=1 git ...`\n'
+            f'- To permanently silence this, install pre-commit with the '
+            f'--allow-missing-config option\n'
+            f'- To uninstall pre-commit run '
+            f'`pre-commit uninstall`',
         )
 
 
@@ -127,7 +123,7 @@ def _pre_push(stdin: bytes) -> Tuple[str, ...]:
     remote = sys.argv[1]
 
     opts: Tuple[str, ...] = ()
-    for line in stdin.decode('UTF-8').splitlines():
+    for line in stdin.decode().splitlines():
         _, local_sha, _, remote_sha = line.split()
         if local_sha == Z40:
             continue
diff --git a/pre_commit/staged_files_only.py b/pre_commit/staged_files_only.py
index 7f3fff0a..22608e59 100644
--- a/pre_commit/staged_files_only.py
+++ b/pre_commit/staged_files_only.py
@@ -8,7 +8,6 @@ from pre_commit import git
 from pre_commit.util import CalledProcessError
 from pre_commit.util import cmd_output
 from pre_commit.util import cmd_output_b
-from pre_commit.util import mkdirp
 from pre_commit.xargs import xargs
 
 
@@ -48,14 +47,14 @@ def _unstaged_changes_cleared(patch_dir: str) -> Generator[None, None, None]:
         retcode=None,
     )
     if retcode and diff_stdout_binary.strip():
-        patch_filename = 'patch{}'.format(int(time.time()))
+        patch_filename = f'patch{int(time.time())}'
         patch_filename = os.path.join(patch_dir, patch_filename)
         logger.warning('Unstaged files detected.')
         logger.info(
             f'Stashing unstaged files to {patch_filename}.',
         )
         # Save the current unstaged changes as a patch
-        mkdirp(patch_dir)
+        os.makedirs(patch_dir, exist_ok=True)
         with open(patch_filename, 'wb') as patch_file:
             patch_file.write(diff_stdout_binary)
 
diff --git a/pre_commit/store.py b/pre_commit/store.py
index 407723c8..4af16193 100644
--- a/pre_commit/store.py
+++ b/pre_commit/store.py
@@ -16,7 +16,6 @@ from pre_commit import git
 from pre_commit.util import CalledProcessError
 from pre_commit.util import clean_path_on_failure
 from pre_commit.util import cmd_output_b
-from pre_commit.util import mkdirp
 from pre_commit.util import resource_text
 from pre_commit.util import rmtree
 
@@ -45,7 +44,7 @@ class Store:
         self.db_path = os.path.join(self.directory, 'db.db')
 
         if not os.path.exists(self.directory):
-            mkdirp(self.directory)
+            os.makedirs(self.directory, exist_ok=True)
             with open(os.path.join(self.directory, 'README'), 'w') as f:
                 f.write(
                     'This directory is maintained by the pre-commit project.\n'
@@ -102,7 +101,7 @@ class Store:
     @classmethod
     def db_repo_name(cls, repo: str, deps: Sequence[str]) -> str:
         if deps:
-            return '{}:{}'.format(repo, ','.join(sorted(deps)))
+            return f'{repo}:{",".join(sorted(deps))}'
         else:
             return repo
 
diff --git a/pre_commit/util.py b/pre_commit/util.py
index 208ce497..dfe07ea9 100644
--- a/pre_commit/util.py
+++ b/pre_commit/util.py
@@ -17,7 +17,6 @@ from typing import Tuple
 from typing import Type
 from typing import Union
 
-from pre_commit import five
 from pre_commit import parse_shebang
 
 if sys.version_info >= (3, 7):  # pragma: no cover (PY37+)
@@ -30,14 +29,6 @@ else:  # pragma: no cover (<PY37)
 EnvironT = Union[Dict[str, str], 'os._Environ']
 
 
-def mkdirp(path: str) -> None:
-    try:
-        os.makedirs(path)
-    except OSError:
-        if not os.path.exists(path):
-            raise
-
-
 @contextlib.contextmanager
 def clean_path_on_failure(path: str) -> Generator[None, None, None]:
     """Cleans up the directory on an exceptional failure."""
@@ -49,11 +40,6 @@ def clean_path_on_failure(path: str) -> Generator[None, None, None]:
         raise
 
 
-@contextlib.contextmanager
-def noop_context() -> Generator[None, None, None]:
-    yield
-
-
 @contextlib.contextmanager
 def tmpdir() -> Generator[str, None, None]:
     """Contextmanager to create a temporary directory.  It will be cleaned up
@@ -76,9 +62,8 @@ def resource_text(filename: str) -> str:
 
 def make_executable(filename: str) -> None:
     original_mode = os.stat(filename).st_mode
-    os.chmod(
-        filename, original_mode | stat.S_IXUSR | stat.S_IXGRP | stat.S_IXOTH,
-    )
+    new_mode = original_mode | stat.S_IXUSR | stat.S_IXGRP | stat.S_IXOTH
+    os.chmod(filename, new_mode)
 
 
 class CalledProcessError(RuntimeError):
@@ -105,40 +90,28 @@ class CalledProcessError(RuntimeError):
                 return b' (none)'
 
         return b''.join((
-            'command: {!r}\n'
-            'return code: {}\n'
-            'expected return code: {}\n'.format(
-                self.cmd, self.returncode, self.expected_returncode,
-            ).encode('UTF-8'),
+            f'command: {self.cmd!r}\n'.encode(),
+            f'return code: {self.returncode}\n'.encode(),
+            f'expected return code: {self.expected_returncode}\n'.encode(),
             b'stdout:', _indent_or_none(self.stdout), b'\n',
             b'stderr:', _indent_or_none(self.stderr),
         ))
 
     def __str__(self) -> str:
-        return self.__bytes__().decode('UTF-8')
+        return self.__bytes__().decode()
 
 
-def _cmd_kwargs(
-        *cmd: str,
-        **kwargs: Any,
-) -> Tuple[Tuple[str, ...], Dict[str, Any]]:
-    # py2/py3 on windows are more strict about the types here
-    cmd = tuple(five.n(arg) for arg in cmd)
-    kwargs['env'] = {
-        five.n(key): five.n(value)
-        for key, value in kwargs.pop('env', {}).items()
-    } or None
+def _setdefault_kwargs(kwargs: Dict[str, Any]) -> None:
     for arg in ('stdin', 'stdout', 'stderr'):
         kwargs.setdefault(arg, subprocess.PIPE)
-    return cmd, kwargs
 
 
 def cmd_output_b(
         *cmd: str,
+        retcode: Optional[int] = 0,
         **kwargs: Any,
 ) -> Tuple[int, bytes, Optional[bytes]]:
-    retcode = kwargs.pop('retcode', 0)
-    cmd, kwargs = _cmd_kwargs(*cmd, **kwargs)
+    _setdefault_kwargs(kwargs)
 
     try:
         cmd = parse_shebang.normalize_cmd(cmd)
@@ -157,8 +130,8 @@ def cmd_output_b(
 
 def cmd_output(*cmd: str, **kwargs: Any) -> Tuple[int, str, Optional[str]]:
     returncode, stdout_b, stderr_b = cmd_output_b(*cmd, **kwargs)
-    stdout = stdout_b.decode('UTF-8') if stdout_b is not None else None
-    stderr = stderr_b.decode('UTF-8') if stderr_b is not None else None
+    stdout = stdout_b.decode() if stdout_b is not None else None
+    stderr = stderr_b.decode() if stderr_b is not None else None
     return returncode, stdout, stderr
 
 
@@ -203,11 +176,12 @@ if os.name != 'nt':  # pragma: windows no cover
 
     def cmd_output_p(
             *cmd: str,
+            retcode: Optional[int] = 0,
             **kwargs: Any,
     ) -> Tuple[int, bytes, Optional[bytes]]:
-        assert kwargs.pop('retcode') is None
+        assert retcode is None
         assert kwargs['stderr'] == subprocess.STDOUT, kwargs['stderr']
-        cmd, kwargs = _cmd_kwargs(*cmd, **kwargs)
+        _setdefault_kwargs(kwargs)
 
         try:
             cmd = parse_shebang.normalize_cmd(cmd)
diff --git a/pre_commit/xargs.py b/pre_commit/xargs.py
index ce20d601..5235dc65 100644
--- a/pre_commit/xargs.py
+++ b/pre_commit/xargs.py
@@ -49,7 +49,6 @@ def _command_length(*cmd: str) -> int:
     # win32 uses the amount of characters, more details at:
     # https://github.com/pre-commit/pre-commit/pull/839
     if sys.platform == 'win32':
-        # the python2.x apis require bytes, we encode as UTF-8
         return len(full_cmd.encode('utf-16le')) // 2
     else:
         return len(full_cmd.encode(sys.getfilesystemencoding()))
@@ -118,6 +117,10 @@ def _thread_mapper(maxsize: int) -> Generator[
 def xargs(
         cmd: Tuple[str, ...],
         varargs: Sequence[str],
+        *,
+        color: bool = False,
+        target_concurrency: int = 1,
+        _max_length: int = _get_platform_max_length(),
         **kwargs: Any,
 ) -> Tuple[int, bytes]:
     """A simplified implementation of xargs.
@@ -125,9 +128,6 @@ def xargs(
     color: Make a pty if on a platform that supports it
     target_concurrency: Target number of partitions to run concurrently
     """
-    color = kwargs.pop('color', False)
-    target_concurrency = kwargs.pop('target_concurrency', 1)
-    max_length = kwargs.pop('_max_length', _get_platform_max_length())
     cmd_fn = cmd_output_p if color else cmd_output_b
     retcode = 0
     stdout = b''
@@ -137,7 +137,7 @@ def xargs(
     except parse_shebang.ExecutableNotFoundError as e:
         return e.to_output()[:2]
 
-    partitions = partition(cmd, varargs, target_concurrency, max_length)
+    partitions = partition(cmd, varargs, target_concurrency, _max_length)
 
     def run_cmd_partition(
             run_cmd: Tuple[str, ...],
diff --git a/testing/resources/arbitrary_bytes_repo/hook.sh b/testing/resources/arbitrary_bytes_repo/hook.sh
index fb7dbae1..9df0c5a0 100755
--- a/testing/resources/arbitrary_bytes_repo/hook.sh
+++ b/testing/resources/arbitrary_bytes_repo/hook.sh
@@ -1,7 +1,7 @@
 #!/usr/bin/env bash
 # Intentionally write mixed encoding to the output.  This should not crash
 # pre-commit and should write bytes to the output.
-# '☃'.encode('UTF-8') + '²'.encode('latin1')
+# '☃'.encode() + '²'.encode('latin1')
 echo -e '\xe2\x98\x83\xb2'
 # exit 1 to trigger printing
 exit 1
diff --git a/testing/resources/stdout_stderr_repo/stdout-stderr-entry b/testing/resources/stdout_stderr_repo/stdout-stderr-entry
index d383c191..7563df53 100755
--- a/testing/resources/stdout_stderr_repo/stdout-stderr-entry
+++ b/testing/resources/stdout_stderr_repo/stdout-stderr-entry
@@ -1,13 +1,7 @@
-#!/usr/bin/env python
-import sys
-
-
-def main():
-    for i in range(6):
-        f = sys.stdout if i % 2 == 0 else sys.stderr
-        f.write(f'{i}\n')
-        f.flush()
-
-
-if __name__ == '__main__':
-    exit(main())
+#!/usr/bin/env bash
+echo 0
+echo 1 1>&2
+echo 2
+echo 3 1>&2
+echo 4
+echo 5 1>&2
diff --git a/testing/resources/stdout_stderr_repo/tty-check-entry b/testing/resources/stdout_stderr_repo/tty-check-entry
index 8c6530ec..01a9d388 100755
--- a/testing/resources/stdout_stderr_repo/tty-check-entry
+++ b/testing/resources/stdout_stderr_repo/tty-check-entry
@@ -1,12 +1,11 @@
-#!/usr/bin/env python
-import sys
-
-
-def main():
-    print('stdin: {}'.format(sys.stdin.isatty()))
-    print('stdout: {}'.format(sys.stdout.isatty()))
-    print('stderr: {}'.format(sys.stderr.isatty()))
-
-
-if __name__ == '__main__':
-    exit(main())
+#!/usr/bin/env bash
+t() {
+    if [ -t "$1" ]; then
+        echo "$2: True"
+    else
+        echo "$2: False"
+    fi
+}
+t 0 stdin
+t 1 stdout
+t 2 stderr
diff --git a/testing/util.py b/testing/util.py
index dbe475eb..0c2cc6a8 100644
--- a/testing/util.py
+++ b/testing/util.py
@@ -1,7 +1,6 @@
 import contextlib
 import os.path
 import subprocess
-import sys
 
 import pytest
 
@@ -18,13 +17,15 @@ def get_resource_path(path):
     return os.path.join(TESTING_DIR, 'resources', path)
 
 
-def cmd_output_mocked_pre_commit_home(*args, **kwargs):
-    # keyword-only argument
-    tempdir_factory = kwargs.pop('tempdir_factory')
-    pre_commit_home = kwargs.pop('pre_commit_home', tempdir_factory.get())
+def cmd_output_mocked_pre_commit_home(
+        *args, tempdir_factory, pre_commit_home=None, env=None, **kwargs,
+):
+    if pre_commit_home is None:
+        pre_commit_home = tempdir_factory.get()
+    env = env if env is not None else os.environ
     kwargs.setdefault('stderr', subprocess.STDOUT)
     # Don't want to write to the home directory
-    env = dict(kwargs.pop('env', os.environ), PRE_COMMIT_HOME=pre_commit_home)
+    env = dict(env, PRE_COMMIT_HOME=pre_commit_home)
     ret, out, _ = cmd_output(*args, env=env, **kwargs)
     return ret, out.replace('\r\n', '\n'), None
 
@@ -44,33 +45,6 @@ xfailif_windows_no_ruby = pytest.mark.xfail(
 xfailif_windows = pytest.mark.xfail(os.name == 'nt', reason='windows')
 
 
-def broken_deep_listdir():  # pragma: no cover (platform specific)
-    if sys.platform != 'win32':
-        return False
-    try:
-        os.listdir('\\\\?\\' + os.path.abspath('.'))
-    except OSError:
-        return True
-    try:
-        os.listdir(b'\\\\?\\C:' + b'\\' * 300)
-    except TypeError:
-        return True
-    except OSError:
-        return False
-
-
-xfailif_broken_deep_listdir = pytest.mark.xfail(
-    broken_deep_listdir(),
-    reason='Node on windows requires deep listdir',
-)
-
-
-xfailif_no_symlink = pytest.mark.xfail(
-    not hasattr(os, 'symlink'),
-    reason='Symlink is not supported on this platform',
-)
-
-
 def supports_venv():  # pragma: no cover (platform specific)
     try:
         __import__('ensurepip')
@@ -123,9 +97,7 @@ def cwd(path):
         os.chdir(original_cwd)
 
 
-def git_commit(*args, **kwargs):
-    fn = kwargs.pop('fn', cmd_output)
-    msg = kwargs.pop('msg', 'commit!')
+def git_commit(*args, fn=cmd_output, msg='commit!', **kwargs):
     kwargs.setdefault('stderr', subprocess.STDOUT)
 
     cmd = ('git', 'commit', '--allow-empty', '--no-gpg-sign', '-a') + args
diff --git a/tests/clientlib_test.py b/tests/clientlib_test.py
index 8499c3dd..c48adbde 100644
--- a/tests/clientlib_test.py
+++ b/tests/clientlib_test.py
@@ -291,13 +291,11 @@ def test_minimum_pre_commit_version_failing():
         cfg = {'repos': [], 'minimum_pre_commit_version': '999'}
         cfgv.validate(cfg, CONFIG_SCHEMA)
     assert str(excinfo.value) == (
-        '\n'
-        '==> At Config()\n'
-        '==> At key: minimum_pre_commit_version\n'
-        '=====> pre-commit version 999 is required but version {} is '
-        'installed.  Perhaps run `pip install --upgrade pre-commit`.'.format(
-            C.VERSION,
-        )
+        f'\n'
+        f'==> At Config()\n'
+        f'==> At key: minimum_pre_commit_version\n'
+        f'=====> pre-commit version 999 is required but version {C.VERSION} '
+        f'is installed.  Perhaps run `pip install --upgrade pre-commit`.'
     )
 
 
diff --git a/tests/commands/autoupdate_test.py b/tests/commands/autoupdate_test.py
index b126cff7..2c7b2f1f 100644
--- a/tests/commands/autoupdate_test.py
+++ b/tests/commands/autoupdate_test.py
@@ -1,4 +1,4 @@
-import pipes
+import shlex
 
 import pytest
 
@@ -118,12 +118,12 @@ def test_rev_info_update_does_not_freeze_if_already_sha(out_of_date):
 
 def test_autoupdate_up_to_date_repo(up_to_date, tmpdir, store):
     contents = (
-        'repos:\n'
-        '-   repo: {}\n'
-        '    rev: {}\n'
-        '    hooks:\n'
-        '    -   id: foo\n'
-    ).format(up_to_date, git.head_rev(up_to_date))
+        f'repos:\n'
+        f'-   repo: {up_to_date}\n'
+        f'    rev: {git.head_rev(up_to_date)}\n'
+        f'    hooks:\n'
+        f'    -   id: foo\n'
+    )
     cfg = tmpdir.join(C.CONFIG_FILE)
     cfg.write(contents)
 
@@ -278,7 +278,7 @@ def test_loses_formatting_when_not_detectable(out_of_date, store, tmpdir):
         '        ],\n'
         '    }}\n'
         ']\n'.format(
-            pipes.quote(out_of_date.path), out_of_date.original_rev,
+            shlex.quote(out_of_date.path), out_of_date.original_rev,
         )
     )
     cfg = tmpdir.join(C.CONFIG_FILE)
@@ -286,12 +286,12 @@ def test_loses_formatting_when_not_detectable(out_of_date, store, tmpdir):
 
     assert autoupdate(str(cfg), store, freeze=False, tags_only=False) == 0
     expected = (
-        'repos:\n'
-        '-   repo: {}\n'
-        '    rev: {}\n'
-        '    hooks:\n'
-        '    -   id: foo\n'
-    ).format(out_of_date.path, out_of_date.head_rev)
+        f'repos:\n'
+        f'-   repo: {out_of_date.path}\n'
+        f'    rev: {out_of_date.head_rev}\n'
+        f'    hooks:\n'
+        f'    -   id: foo\n'
+    )
     assert cfg.read() == expected
 
 
@@ -358,12 +358,12 @@ def test_hook_disppearing_repo_raises(hook_disappearing, store):
 
 def test_autoupdate_hook_disappearing_repo(hook_disappearing, tmpdir, store):
     contents = (
-        'repos:\n'
-        '-   repo: {}\n'
-        '    rev: {}\n'
-        '    hooks:\n'
-        '    -   id: foo\n'
-    ).format(hook_disappearing.path, hook_disappearing.original_rev)
+        f'repos:\n'
+        f'-   repo: {hook_disappearing.path}\n'
+        f'    rev: {hook_disappearing.original_rev}\n'
+        f'    hooks:\n'
+        f'    -   id: foo\n'
+    )
     cfg = tmpdir.join(C.CONFIG_FILE)
     cfg.write(contents)
 
diff --git a/tests/commands/install_uninstall_test.py b/tests/commands/install_uninstall_test.py
index feef316e..c611bfb6 100644
--- a/tests/commands/install_uninstall_test.py
+++ b/tests/commands/install_uninstall_test.py
@@ -14,7 +14,6 @@ from pre_commit.commands.install_uninstall import uninstall
 from pre_commit.parse_shebang import find_executable
 from pre_commit.util import cmd_output
 from pre_commit.util import make_executable
-from pre_commit.util import mkdirp
 from pre_commit.util import resource_text
 from testing.fixtures import git_dir
 from testing.fixtures import make_consuming_repo
@@ -22,7 +21,6 @@ from testing.fixtures import remove_config_from_repo
 from testing.util import cmd_output_mocked_pre_commit_home
 from testing.util import cwd
 from testing.util import git_commit
-from testing.util import xfailif_no_symlink
 from testing.util import xfailif_windows
 
 
@@ -52,11 +50,11 @@ def test_shebang_posix_not_on_path():
 
 
 def test_shebang_posix_on_path(tmpdir):
-    tmpdir.join('python{}'.format(sys.version_info[0])).ensure()
+    tmpdir.join(f'python{sys.version_info[0]}').ensure()
 
     with mock.patch.object(sys, 'platform', 'posix'):
         with mock.patch.object(os, 'defpath', tmpdir.strpath):
-            expected = '#!/usr/bin/env python{}'.format(sys.version_info[0])
+            expected = f'#!/usr/bin/env python{sys.version_info[0]}'
             assert shebang() == expected
 
 
@@ -90,7 +88,6 @@ def test_install_refuses_core_hookspath(in_git_dir, store):
     assert install(C.CONFIG_FILE, store, hook_types=['pre-commit'])
 
 
-@xfailif_no_symlink  # pragma: windows no cover
 def test_install_hooks_dead_symlink(in_git_dir, store):
     hook = in_git_dir.join('.git/hooks').ensure_dir().join('pre-commit')
     os.symlink('/fake/baz', hook.strpath)
@@ -307,7 +304,7 @@ EXISTING_COMMIT_RUN = re.compile(
 
 
 def _write_legacy_hook(path):
-    mkdirp(os.path.join(path, '.git/hooks'))
+    os.makedirs(os.path.join(path, '.git/hooks'), exist_ok=True)
     with open(os.path.join(path, '.git/hooks/pre-commit'), 'w') as f:
         f.write('#!/usr/bin/env bash\necho "legacy hook"\n')
     make_executable(f.name)
@@ -370,7 +367,7 @@ def test_failing_existing_hook_returns_1(tempdir_factory, store):
     path = make_consuming_repo(tempdir_factory, 'script_hooks_repo')
     with cwd(path):
         # Write out a failing "old" hook
-        mkdirp(os.path.join(path, '.git/hooks'))
+        os.makedirs(os.path.join(path, '.git/hooks'), exist_ok=True)
         with open(os.path.join(path, '.git/hooks/pre-commit'), 'w') as f:
             f.write('#!/usr/bin/env bash\necho "fail!"\nexit 1\n')
         make_executable(f.name)
@@ -432,7 +429,7 @@ def test_replace_old_commit_script(tempdir_factory, store):
             CURRENT_HASH, PRIOR_HASHES[-1],
         )
 
-        mkdirp(os.path.join(path, '.git/hooks'))
+        os.makedirs(os.path.join(path, '.git/hooks'), exist_ok=True)
         with open(os.path.join(path, '.git/hooks/pre-commit'), 'w') as f:
             f.write(new_contents)
         make_executable(f.name)
@@ -609,7 +606,7 @@ def test_pre_push_legacy(tempdir_factory, store):
     path = tempdir_factory.get()
     cmd_output('git', 'clone', upstream, path)
     with cwd(path):
-        mkdirp(os.path.join(path, '.git/hooks'))
+        os.makedirs(os.path.join(path, '.git/hooks'), exist_ok=True)
         with open(os.path.join(path, '.git/hooks/pre-push'), 'w') as f:
             f.write(
                 '#!/usr/bin/env bash\n'
@@ -658,7 +655,7 @@ def test_commit_msg_integration_passing(
 
 def test_commit_msg_legacy(commit_msg_repo, tempdir_factory, store):
     hook_path = os.path.join(commit_msg_repo, '.git/hooks/commit-msg')
-    mkdirp(os.path.dirname(hook_path))
+    os.makedirs(os.path.dirname(hook_path), exist_ok=True)
     with open(hook_path, 'w') as hook_file:
         hook_file.write(
             '#!/usr/bin/env bash\n'
@@ -713,7 +710,7 @@ def test_prepare_commit_msg_legacy(
     hook_path = os.path.join(
         prepare_commit_msg_repo, '.git/hooks/prepare-commit-msg',
     )
-    mkdirp(os.path.dirname(hook_path))
+    os.makedirs(os.path.dirname(hook_path), exist_ok=True)
     with open(hook_path, 'w') as hook_file:
         hook_file.write(
             '#!/usr/bin/env bash\n'
diff --git a/tests/commands/run_test.py b/tests/commands/run_test.py
index d271575e..1ed866bc 100644
--- a/tests/commands/run_test.py
+++ b/tests/commands/run_test.py
@@ -1,5 +1,5 @@
 import os.path
-import pipes
+import shlex
 import sys
 import time
 from unittest import mock
@@ -27,7 +27,6 @@ from testing.util import cmd_output_mocked_pre_commit_home
 from testing.util import cwd
 from testing.util import git_commit
 from testing.util import run_opts
-from testing.util import xfailif_no_symlink
 
 
 @pytest.fixture
@@ -580,8 +579,7 @@ def test_lots_of_files(store, tempdir_factory):
 
         # Write a crap ton of files
         for i in range(400):
-            filename = '{}{}'.format('a' * 100, i)
-            open(filename, 'w').close()
+            open(f'{"a" * 100}{i}', 'w').close()
 
         cmd_output('git', 'add', '.')
         install(C.CONFIG_FILE, store, hook_types=['pre-commit'])
@@ -673,7 +671,7 @@ def test_local_hook_passes(cap_out, store, repo_with_passing_hook):
                 'id': 'identity-copy',
                 'name': 'identity-copy',
                 'entry': '{} -m pre_commit.meta_hooks.identity'.format(
-                    pipes.quote(sys.executable),
+                    shlex.quote(sys.executable),
                 ),
                 'language': 'system',
                 'files': r'\.py$',
@@ -862,7 +860,6 @@ def test_include_exclude_base_case(some_filenames):
     ]
 
 
-@xfailif_no_symlink  # pragma: windows no cover
 def test_matches_broken_symlink(tmpdir):
     with tmpdir.as_cwd():
         os.symlink('does-not-exist', 'link')
@@ -893,7 +890,7 @@ def test_args_hook_only(cap_out, store, repo_with_passing_hook):
                 'id': 'identity-copy',
                 'name': 'identity-copy',
                 'entry': '{} -m pre_commit.meta_hooks.identity'.format(
-                    pipes.quote(sys.executable),
+                    shlex.quote(sys.executable),
                 ),
                 'language': 'system',
                 'files': r'\.py$',
diff --git a/tests/conftest.py b/tests/conftest.py
index 21a3034f..335d2614 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -249,17 +249,16 @@ class Fixture:
 
     def get(self):
         """Get the output assuming it was written as UTF-8 bytes"""
-        return self.get_bytes().decode('UTF-8')
+        return self.get_bytes().decode()
 
 
 @pytest.fixture
 def cap_out():
     stream = FakeStream()
     write = functools.partial(output.write, stream=stream)
-    write_line = functools.partial(output.write_line, stream=stream)
-    with mock.patch.object(output, 'write', write):
-        with mock.patch.object(output, 'write_line', write_line):
-            yield Fixture(stream)
+    write_line_b = functools.partial(output.write_line_b, stream=stream)
+    with mock.patch.multiple(output, write=write, write_line_b=write_line_b):
+        yield Fixture(stream)
 
 
 @pytest.fixture
diff --git a/tests/envcontext_test.py b/tests/envcontext_test.py
index 56dd2632..f9d4dce6 100644
--- a/tests/envcontext_test.py
+++ b/tests/envcontext_test.py
@@ -8,12 +8,7 @@ from pre_commit.envcontext import UNSET
 from pre_commit.envcontext import Var
 
 
-def _test(**kwargs):
-    before = kwargs.pop('before')
-    patch = kwargs.pop('patch')
-    expected = kwargs.pop('expected')
-    assert not kwargs
-
+def _test(*, before, patch, expected):
     env = before.copy()
     with envcontext(patch, _env=env):
         assert env == expected
diff --git a/tests/error_handler_test.py b/tests/error_handler_test.py
index fa2fc2d3..8fa41a70 100644
--- a/tests/error_handler_test.py
+++ b/tests/error_handler_test.py
@@ -99,9 +99,7 @@ def test_log_and_exit(cap_out, mock_store_dir):
 
     printed = cap_out.get()
     log_file = os.path.join(mock_store_dir, 'pre-commit.log')
-    assert printed == (
-        'msg: FatalError: hai\n' 'Check the log at {}\n'.format(log_file)
-    )
+    assert printed == f'msg: FatalError: hai\nCheck the log at {log_file}\n'
 
     assert os.path.exists(log_file)
     with open(log_file) as f:
diff --git a/tests/languages/ruby_test.py b/tests/languages/ruby_test.py
index 497b01d6..36a029d1 100644
--- a/tests/languages/ruby_test.py
+++ b/tests/languages/ruby_test.py
@@ -1,7 +1,6 @@
 import os.path
-import pipes
 
-from pre_commit.languages.ruby import _install_rbenv
+from pre_commit.languages import ruby
 from pre_commit.prefix import Prefix
 from pre_commit.util import cmd_output
 from testing.util import xfailif_windows_no_ruby
@@ -10,31 +9,20 @@ from testing.util import xfailif_windows_no_ruby
 @xfailif_windows_no_ruby
 def test_install_rbenv(tempdir_factory):
     prefix = Prefix(tempdir_factory.get())
-    _install_rbenv(prefix)
+    ruby._install_rbenv(prefix)
     # Should have created rbenv directory
     assert os.path.exists(prefix.path('rbenv-default'))
-    # We should have created our `activate` script
-    activate_path = prefix.path('rbenv-default', 'bin', 'activate')
-    assert os.path.exists(activate_path)
 
     # Should be able to activate using our script and access rbenv
-    cmd_output(
-        'bash', '-c',
-        '. {} && rbenv --help'.format(
-            pipes.quote(prefix.path('rbenv-default', 'bin', 'activate')),
-        ),
-    )
+    with ruby.in_env(prefix, 'default'):
+        cmd_output('rbenv', '--help')
 
 
 @xfailif_windows_no_ruby
 def test_install_rbenv_with_version(tempdir_factory):
     prefix = Prefix(tempdir_factory.get())
-    _install_rbenv(prefix, version='1.9.3p547')
+    ruby._install_rbenv(prefix, version='1.9.3p547')
 
     # Should be able to activate and use rbenv install
-    cmd_output(
-        'bash', '-c',
-        '. {} && rbenv install --help'.format(
-            pipes.quote(prefix.path('rbenv-1.9.3p547', 'bin', 'activate')),
-        ),
-    )
+    with ruby.in_env(prefix, '1.9.3p547'):
+        cmd_output('rbenv', 'install', '--help')
diff --git a/tests/parse_shebang_test.py b/tests/parse_shebang_test.py
index 7a958b01..158e5719 100644
--- a/tests/parse_shebang_test.py
+++ b/tests/parse_shebang_test.py
@@ -23,7 +23,7 @@ def test_file_doesnt_exist():
 
 def test_simple_case(tmpdir):
     x = tmpdir.join('f')
-    x.write_text('#!/usr/bin/env echo', encoding='UTF-8')
+    x.write('#!/usr/bin/env echo')
     make_executable(x.strpath)
     assert parse_shebang.parse_filename(x.strpath) == ('echo',)
 
diff --git a/tests/repository_test.py b/tests/repository_test.py
index 5c541c66..2dc9e866 100644
--- a/tests/repository_test.py
+++ b/tests/repository_test.py
@@ -10,7 +10,6 @@ import cfgv
 import pytest
 
 import pre_commit.constants as C
-from pre_commit import five
 from pre_commit.clientlib import CONFIG_SCHEMA
 from pre_commit.clientlib import load_manifest
 from pre_commit.envcontext import envcontext
@@ -33,7 +32,6 @@ from testing.util import cwd
 from testing.util import get_resource_path
 from testing.util import skipif_cant_run_docker
 from testing.util import skipif_cant_run_swift
-from testing.util import xfailif_broken_deep_listdir
 from testing.util import xfailif_no_venv
 from testing.util import xfailif_windows_no_ruby
 
@@ -119,7 +117,7 @@ def test_python_hook(tempdir_factory, store):
     _test_hook_repo(
         tempdir_factory, store, 'python_hooks_repo',
         'foo', [os.devnull],
-        b"['" + five.to_bytes(os.devnull) + b"']\nHello World\n",
+        f'[{os.devnull!r}]\nHello World\n'.encode(),
     )
 
 
@@ -154,7 +152,7 @@ def test_python_hook_weird_setup_cfg(in_git_dir, tempdir_factory, store):
     _test_hook_repo(
         tempdir_factory, store, 'python_hooks_repo',
         'foo', [os.devnull],
-        b"['" + five.to_bytes(os.devnull) + b"']\nHello World\n",
+        f'[{os.devnull!r}]\nHello World\n'.encode(),
     )
 
 
@@ -163,7 +161,7 @@ def test_python_venv(tempdir_factory, store):  # pragma: no cover (no venv)
     _test_hook_repo(
         tempdir_factory, store, 'python_venv_hooks_repo',
         'foo', [os.devnull],
-        b"['" + five.to_bytes(os.devnull) + b"']\nHello World\n",
+        f'[{os.devnull!r}]\nHello World\n'.encode(),
     )
 
 
@@ -188,7 +186,7 @@ def test_versioned_python_hook(tempdir_factory, store):
         tempdir_factory, store, 'python3_hooks_repo',
         'python3-hook',
         [os.devnull],
-        b"3\n['" + five.to_bytes(os.devnull) + b"']\nHello World\n",
+        f'3\n[{os.devnull!r}]\nHello World\n'.encode(),
     )
 
 
@@ -231,7 +229,6 @@ def test_run_a_docker_image_hook(tempdir_factory, store, hook_id):
     )
 
 
-@xfailif_broken_deep_listdir
 def test_run_a_node_hook(tempdir_factory, store):
     _test_hook_repo(
         tempdir_factory, store, 'node_hooks_repo',
@@ -239,7 +236,6 @@ def test_run_a_node_hook(tempdir_factory, store):
     )
 
 
-@xfailif_broken_deep_listdir
 def test_run_versioned_node_hook(tempdir_factory, store):
     _test_hook_repo(
         tempdir_factory, store, 'node_versioned_hooks_repo',
@@ -522,7 +518,6 @@ def test_additional_ruby_dependencies_installed(tempdir_factory, store):
         assert 'tins' in output
 
 
-@xfailif_broken_deep_listdir  # pragma: windows no cover
 def test_additional_node_dependencies_installed(tempdir_factory, store):
     path = make_repo(tempdir_factory, 'node_hooks_repo')
     config = make_config_from_repo(path)
@@ -805,9 +800,9 @@ def test_hook_id_not_present(tempdir_factory, store, fake_log_handler):
     with pytest.raises(SystemExit):
         _get_hook(config, store, 'i-dont-exist')
     assert fake_log_handler.handle.call_args[0][0].msg == (
-        '`i-dont-exist` is not present in repository file://{}.  '
-        'Typo? Perhaps it is introduced in a newer version?  '
-        'Often `pre-commit autoupdate` fixes this.'.format(path)
+        f'`i-dont-exist` is not present in repository file://{path}.  '
+        f'Typo? Perhaps it is introduced in a newer version?  '
+        f'Often `pre-commit autoupdate` fixes this.'
     )