Fatal error: Uncaught Error: Class "Symfony\Component\Notifier\Transport\RoundRobinTransport" not found in I:\www\frameworks\Symfony\doctrine\vendor\symfony\notifier\Transport\FailoverTransport.php:21 Stack trace: #0 {main} thrown in I:\www\frameworks\Symfony\doctrine\vendor\symfony\notifier\Transport\FailoverTransport.php on line 21