Fatal error: Uncaught Error: Class 'Symfony\Contracts\EventDispatcher\Event' not found in /home/users/00/3c/21/home/www/vendor/kevinpapst/adminlte-bundle/Event/ThemeEvent.php:17 Stack trace: #0 {main} thrown in /home/users/00/3c/21/home/www/vendor/kevinpapst/adminlte-bundle/Event/ThemeEvent.php on line 17