def __missing__(self, key):
        if self.default_factory is None:
            raise KeyError(key)
        else:
            ret = self[key] = self.default_factory(name=key)
            return ret
def do_register_opts(opts, group=None, ignore_errors=False):
    try:
        cfg.CONF.register_opts(opts, group=group)
    except:
        if not ignore_errors:
            raise