Fatal error: Uncaught Error: Class "Drupal\Core\EventSubscriber\HttpExceptionSubscriberBase" not found in /home/www/drupal8/test/core/modules/serialization/src/EventSubscriber/DefaultExceptionSubscriber.php:15 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/serialization/src/EventSubscriber/DefaultExceptionSubscriber.php on line 15