Copy of apple/swift/utils/update-checkout script

update-checkout

#!/usr/bin/env python3

import sys

import update_checkout

if __name__ == '__main__':
    # This line was added in dfe3af81b2 to address an importing issue on
    # Windows.  It causes this script to break badly when used with
    # Python 3.8 on macOS. Disabling for all Python 3 until someone
    # can help sort out what's really needed for Windows:
    if sys.version_info.major < 3:
        sys.modules[__name__] = sys.modules['update_checkout']

    update_checkout.main()