Validate the base classes of the new class to be created,
        making sure none of them are ``@final``.

def _validate_base_classes(meta, bases):
        """Validate the base classes of the new class to be created,
        making sure none of them are ``@final``.
        """
        for base in bases:
            if meta._is_final(base):
                raise ClassError(
                    "cannot inherit from @final class %s" % (base.__name__,))