code: private function failedDispatch($queue, \Exception $error)
      {
          foreach ($queue as $index => $data) {
              $this->clear($data['key']);
              $data['reject']($error);
          }
      }
docs: Do not cache individual loads if the entire batch dispatch fails,
  but still reject each request so they do not hang.
  @param array      $queue
  @param \Exception $error