code: def response_url(self):
          
          url = ""
          url = self.session['lis_outcome_service_url']
          app_config = self.lti_kwargs['app'].config
          urls = app_config.get('PYLTI_URL_FIX', dict())
          # url remapping is useful for using devstack
          # devstack reports httpS://localhost:8000/ and listens on HTTP
          for prefix, mapping in urls.items():
              if url.startswith(prefix):
                  for _from, _to in mapping.items():
                      url = url.replace(_from, _to)
          return url
docs: Returns remapped lis_outcome_service_url
          uses PYLTI_URL_FIX map to support edX dev-stack
  
          :return: remapped lis_outcome_service_url