'Override the routine for allowing the router:external attribute.'

def _create_network(self, fmt, name, admin_state_up, **kwargs):

    new_args = dict(zip(map((lambda x: x.replace('__', ':')), kwargs), kwargs.values()))
    arg_list = (new_args.pop('arg_list', ()) + (external_net.EXTERNAL,))
    return super(ExtNetDBTestCase, self)._create_network(fmt, name, admin_state_up, arg_list=arg_list, **new_args)
