Fatal error: Uncaught Error: Class "Symfony\Component\HttpFoundation\Response" not found in /home/www/drupal8/test/core/lib/Drupal/Core/Form/EnforcedResponse.php:21 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/lib/Drupal/Core/Form/EnforcedResponse.php on line 21