Returns a tuple of (opts, args) for arguments.

def parse_args(argv):
    """Returns a tuple of (opts, args) for arguments."""
    parser = make_parser()

    opts, args = parser.parse_args(argv[1:])

    # Use APPENGINEPY_SDK_VERSION if set.
    if not args and (sdk_version_key in os.environ):
        args = (os.environ[sdk_version_key],)

    return opts, args