code: func isConnErr(err error) bool {
  	if err == nil {
  		return false
  	}
  	if err.Error() == "no Elasticsearch node available" {
  		return true
  	}
  	innerErr := errors.Cause(err)
  	if innerErr == nil {
  		return false
  	}
  	if innerErr.Error() == "no Elasticsearch node available" {
  		return true
  	}
  	return false
  }
docs: // isConnErr returns true if the error indicates that Elastic could not
  // find an Elasticsearch host to connect to.