Fatal error: Uncaught Error: Interface "Symfony\Component\Validator\ConstraintViolationListInterface" not found in /home/www/drupal8/test/core/lib/Drupal/Core/Entity/EntityConstraintViolationListInterface.php:15 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/lib/Drupal/Core/Entity/EntityConstraintViolationListInterface.php on line 15