Fatal error: Uncaught Error: Interface "Symfony\Component\EventDispatcher\EventDispatcherInterface" not found in /home/www/drupal8/test/core/lib/Drupal/Component/EventDispatcher/ContainerAwareEventDispatcher.php:34 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/lib/Drupal/Component/EventDispatcher/ContainerAwareEventDispatcher.php on line 34