From the release notes:
Under OS X, there were reports of problems with flashbake not finding git. This problem was most noticeable while running under cron. OS X 10.5 replaced cron with launchd and provides a pretty stripped down cron-like wrapper to run compatible crontabs but it doesn’t setup the execution environment correctly. Even if you add some env vars to the tab, it still was encountering problems.
This version changes the git calls to use Python’s subprocess module which allows for better control of the execution environment. This version also catches problems finding the git executable raising a clear error. You may now also add the git_path: option to .flashbake to tell flashbake explicitly where to find git.