Use asottile/add-trailing-comma

pre_commit/commands/autoupdate.py

@@ -59,7 +59,7 @@ def _update_repo(repo_config, runner, tags_only):
     if hooks_missing:
         raise RepositoryCannotBeUpdatedError(
             'Cannot update because the tip of master is missing these hooks:\n'
-            '{}'.format(', '.join(sorted(hooks_missing)))
+            '{}'.format(', '.join(sorted(hooks_missing))),
         )
 
     return new_config

pre_commit/commands/install_uninstall.py

@@ -51,7 +51,7 @@ def install(
             'Running in migration mode with existing hooks at {}\n'
             'Use -f to use only pre-commit.'.format(
                 legacy_path,
-            )
+            ),
         )
 
     with io.open(hook_path, 'w') as pre_commit_file_obj:

pre_commit/commands/run.py

@@ -235,7 +235,7 @@ def run(runner, args, environ=os.environ):
             logger.error(
                 'Your .pre-commit-config.yaml is unstaged.\n'
                 '`git add .pre-commit-config.yaml` to fix this.\n'
-                'Run pre-commit with --allow-unstaged-config to silence this.'
+                'Run pre-commit with --allow-unstaged-config to silence this.',
             )
             return 1