'Retrieves response and timestamp for `key` if it\'s stored in cache,
otherwise returns `default`
:param key: key of resource
:param default: return this if `key` not found in cache
:returns: tuple (response, datetime)
.. note:: Response is restored after unpickling with :meth:`restore_response`'

def get_response_and_time(self, key, default=(None, None)):

    try:
        if (key not in self.responses):
            key = self.keys_map[key]
        (response, timestamp) = self.responses[key]
    except KeyError:
        return default
    return (self.restore_response(response), timestamp)
