Fatal error: Uncaught Error: Interface "Symfony\Component\EventDispatcher\EventSubscriberInterface" not found in /home/www/drupal8/test/core/modules/serialization/src/EventSubscriber/BcConfigSubscriber.php:13 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/serialization/src/EventSubscriber/BcConfigSubscriber.php on line 13