Flake8 pre-commit hook

pre-commit

#!/usr/bin/env python

from __future__ import with_statement
import os
import re
import shutil
import subprocess
import sys
import tempfile
from shutil import copyfile


def system(*args, **kwargs):
    kwargs.setdefault('stdout', subprocess.PIPE)
    proc = subprocess.Popen(args, **kwargs)
    out, err = proc.communicate()
    return out


def main():
    modified = re.compile(r'^[AM]+\s+(?P<name>.*\.py)', re.MULTILINE)
    files = system('git', 'status', '--porcelain')
    files = modified.findall(files.decode())

    tempdir = tempfile.mkdtemp()
    config_file = 'setup.cfg'
    if os.path.exists(config_file):
        copyfile(config_file, os.path.join(tempdir, config_file))
    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 open(filename, 'w') as f:
            system('git', 'show', ':' + name, stdout=f)

    output = system('flake8', '.', cwd=tempdir)
    shutil.rmtree(tempdir)
    if output:
        print('Flake8 style violations have been detected. Please fix them\n '
              'or force the commit with "git commit --no-verify".\n')
        print(output,)
        sys.exit(1)


if __name__ == '__main__':
    main()