def METHOD_NAME(source):
    """Move a PEP 3147/488 pyc file to its legacy pyc location.
    :param source: The file system path to the source file.  The source file
        does not need to exist, however the PEP 3147/488 pyc file must exist.
    :return: The file system path to the legacy pyc file.
    """
    pyc_file = importlib.util.cache_from_source(source)
    up_one = os.path.dirname(os.path.abspath(source))
    legacy_pyc = os.path.join(up_one, source + 'c')
    shutil.move(pyc_file, legacy_pyc)
    return legacy_pyc