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