Return (expiration, obj) corresponding to provided url, exercising the
        cache_policy as necessary.

def factory(self, url):
        '''
        Return (expiration, obj) corresponding to provided url, exercising the
        cache_policy as necessary.
        '''
        try:
            return self.fetch(url)
        except BaseException as exc:
            logger.exception('Reppy cache fetch error on %s' % url)
            return self.cache_policy.exception(url, exc)