Replace variable dir with backupdir to avoid shadowing builtin.
Untabify all the things.
Reformat into PEP8 compliance.
Fix things that pylint complains about.
Convert os.system to subprocess.check_output. Converted git options to an array. Incidental
conversion of path creation to use os.path.join.
Replace print with logging.*, adding better reporting down to the debug level. --cron becomes an
alias for --log-level=warn. Report errors and continue to the next repo when git commands fail.