PEP8 pre-commit hook in Python

gistfile1.py

#!/usr/bin/env python
from __future__ import with_statement
import os
import shutil
import subprocess
import sys
import tempfile


def system(*args, **kwargs):
    kwargs.setdefault('stdout', subprocess.PIPE)
    try:
        proc = subprocess.Popen(args, **kwargs)
        out, err = proc.communicate()
    except OSError, e:
        print "error: could not execute %r" % "".join(args)
        sys.exit(1)
    return out


def main():
    fail=False
    files = (file for file in system('git', 'diff', '--name-only', '--staged', '--diff-filter=AM').splitlines() if file.endswith('.py'))

    tempdir = tempfile.mkdtemp()
    for name in files:
        filename = os.path.join(tempdir, name)
        filepath = os.path.dirname(filename)
        if not os.path.exists(filepath):
            os.makedirs(filepath)
        with file(filename, 'w') as f:
            system('git', 'show', ':' + name, stdout=f)

    # run pep8
    print "running hook - pep8"
    output = system('pep8', '.', cwd=tempdir)
    if output:
        fail=True
        print output,

    print "running hook - pyflakes"
    output = system('pyflakes', '.', cwd=tempdir)
    if output:
        fail=True
        print output,

    shutil.rmtree(tempdir)
    if fail:
        sys.exit(1)
    else:
        sys.exit(0)


if __name__ == '__main__':
    main()