code: def _is_reachable(self, server):
          
  
          try:
              server['redis'].ping()
              return True
          except UserWarning:
              self._logger.warn('Cannot reach redis server: ' + server['url'])
          except Exception:
              self._logger.warn('Cannot reach redis server: ' + server['url'])
  
          return False
docs: Checks if the given redis server is reachable