code: func isEtcdErrorNum(err error, errorCode int) bool {
  	if err != nil {
  		if etcdError, ok := err.(etcd.Error); ok {
  			return etcdError.Code == errorCode
  		}
  		// NOTE: There are other error types returned
  	}
  	return false
  }
docs: // isEtcdErrorNum returns true if and only if err is an etcd error, whose errorCode matches errorCode