Fatal error: Uncaught Error: Class "Symfony\Component\Config\Definition\Exception\Exception" not found in I:\www\frameworks\Symfony\doctrine\vendor\symfony\config\Definition\Exception\UnsetKeyException.php:20 Stack trace: #0 {main} thrown in I:\www\frameworks\Symfony\doctrine\vendor\symfony\config\Definition\Exception\UnsetKeyException.php on line 20