For https://github.com/GoogleCloudPlatform/google-cloud-python/pull/2449

whitespace_check.py

import os
import subprocess


IGNORED = (
    'docs/_static/images/favicon.ico',
    'docs/_static/images/gcp-logo-32x32.png',
    'docs/_static/images/gcp-logo.png',
    'system_tests/data/CloudPlatform_128px_Retina.png',
    'system_tests/data/five-point-one-mb-file.zip',
    'system_tests/key.json.enc',
)
MAKEFILES = (
    'Makefile.bigtable_v2',
    'Makefile.datastore',
    'docs/Makefile',
)


def main():
    git_root = subprocess.check_output(
        ['git', 'rev-parse', '--show-toplevel'])
    git_root = git_root.strip()
    os.chdir(git_root)

    all_files = subprocess.check_output(
        ['git', 'ls-files'])
    all_files = all_files.strip().split('\n')

    for filename in all_files:
        if filename in IGNORED:
            continue
        with open(filename, 'rb') as file_obj:
            lines = file_obj.readlines()
            if len(lines) == 0:
                raise ValueError(filename, 'empty file')
            last_line = lines[-1]
            if not last_line.endswith('\n'):
                raise ValueError(filename, 'no end newline')
            if last_line == '\n':
                raise ValueError(filename, 'trailing newline')
            for line in lines:
                if '\r' in line:
                    raise ValueError(filename, line,
                                     'windows linefeed')
                if '\t' in line:
                    if filename not in MAKEFILES:
                        raise ValueError(filename, line,
                                         'tab character')
                if line.rstrip() + '\n' != line:
                    raise ValueError(filename, line,
                                     'trailing whitespace')


if __name__ == '__main__':
    main()