React\Promise\Deferred::reject PHP Method

    public function reject($reason = null)
    {
        $this->promise();
        call_user_func($this->rejectCallback, $reason);
    }

 /**
  * Change the target owner
  * @param Deferred $deferred
  * @param TaskInterface $task
  * @return bool
  */
 protected function processDeferred(Deferred $deferred, TaskInterface $task)
 {
     yield;
     /** @var Description $description */
     $description = $task->getDescription();
     try {
         $deferred->notify(new Notification("Changing '{$description->getTarget()}' owner to '{$description->getOwner()}'", Notification::PRIORITY_NORMAL));
         if ($this->getFileSystem()->changeOwner($description->getTarget(), $description->getOwner())) {
             $deferred->resolve("Changed '{$description->getTarget()}' owner to '{$description->getOwner()}' successfully");
             return;
         }
     } catch (\Exception $e) {
         // do noting, we reject below
         $deferred->reject("Failed to change the owner of {$description->getTarget()}: " . $e->getMessage());
         return;
     }
     $deferred->reject("Failed to change the owner of {$description->getTarget()} to {$description->getOwner()}");
 }