update-git.py

#!/usr/bin/env python

import os
import re
import subprocess

import requests

repo_dir = "{HOME}/src/kitsune".format(**os.environ)
environments = {
    'dev': 'http://support-dev.allizom.org/media/revision.txt',
    'stage': 'http://support.allizom.org/media/revision.txt',
    'prod': 'http://support.mozilla.org/media/revision.txt',
}

def main():
    cdpath = os.path.join(os.path.dirname(os.path.realpath(__file__)), '..')
    os.chdir(cdpath)

    git = Git()

    print(git.fetch(all=True))
    for env_name, revision_url in environments.items():
        try:
            cur_rev = git.rev_parse('deployed/' + env_name).strip()
        except subprocess.CalledProcessError:
            cur_rev = None
        new_rev = requests.get(revision_url).text.strip()

        if cur_rev != new_rev:
            print 'updating ' + env_name, cur_rev[:8], new_rev[:8]
            git.update_ref('refs/heads/deployed/' + env_name, new_rev)

if __name__ == '__main__':
    main()

The Git class import is missing.