code: def remove_host(self, host_id):
          
          with self._lock:
              rv = self._hosts.pop(host_id, None) is not None
              pool = self._pools.pop(host_id, None)
              if pool is not None:
                  pool.disconnect()
              self._hosts_age += 1
              return rv
docs: Removes a host from the client.  This only really useful for
          unittests.