code: def errback(self, herald_svc, exception):
          
          if self.__errback is not None:
              try:
                  # pylint: disable=W0703
                  self.__errback(herald_svc, exception)
              except Exception as ex:
                  _logger.exception("Error calling errback: %s", ex)
docs: Tries to call the error callback of the post message.
          Avoids errors to go outside this method.
  
          :param herald_svc: Herald service instance
          :param exception: An exception describing/caused by the error