code: def handle_backend_error(self, exception):
          
          idp = self._load_idp_dynamic_entity_id(exception.state)
          return self._handle_backend_error(exception, idp)
docs: Loads the frontend entity id dynamically.
          See super class satosa.frontends.saml2.SAMLFrontend#handle_backend_error
          :type exception: satosa.exception.SATOSAAuthenticationError
          :rtype: satosa.response.Response