Fatal error: Uncaught Error: Class 'Symfony\Contracts\EventDispatcher\Event' not found in /home/benjamincb/demos/acdg-site/vendor/contao/installation-bundle/src/Event/InitializeApplicationEvent.php:17 Stack trace: #0 {main} thrown in /home/benjamincb/demos/acdg-site/vendor/contao/installation-bundle/src/Event/InitializeApplicationEvent.php on line 17