message: add Constants[2]
diff: @@ -22,6 +22,7 @@ class Constant
  const EVENT_WORKER_STOP = 'workerStop';
  const EVENT_MANAGER_START = 'managerStart';
  const EVENT_MANAGER_STOP = 'managerStop';
  + const EVENT_ERROR = 'error';
  const OPTION_CHROOT = 'chroot';
  const OPTION_USER = 'user';
  