Allow arbitrary bytes in output. Resolves #245

testing/resources/arbitrary_bytes_repo/hooks.yaml

@@ -0,0 +1,6 @@
+-   id: python3-hook
+    name: Python 3 Hook
+    entry: python3-hook
+    language: python
+    language_version: python3.3
+    files: \.py$

testing/resources/arbitrary_bytes_repo/python3_hook/main.py

@@ -0,0 +1,13 @@
+# -*- coding: utf-8 -*-
+from __future__ import print_function
+from __future__ import unicode_literals
+
+import sys
+
+
+def func():
+    # Intentionally write mixed encoding to the output.  This should not crash
+    # pre-commit and should write bytes to the output.
+    sys.stdout.buffer.write('☃'.encode('UTF-8') + '²'.encode('latin1') + b'\n')
+    # Return 1 to trigger printing
+    return 1

testing/resources/arbitrary_bytes_repo/setup.py

@@ -0,0 +1,11 @@
+from setuptools import find_packages
+from setuptools import setup
+
+setup(
+    name='python3_hook',
+    version='0.0.0',
+    packages=find_packages('.'),
+    entry_points={
+        'console_scripts': ['python3-hook = python3_hook.main:func'],
+    },
+)