Fatal error: Uncaught Error: Class "Symfony\Component\DependencyInjection\ContainerBuilder" not found in /home/www/drupal8/test/core/lib/Drupal/Core/DependencyInjection/ContainerBuilder.php:19 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/lib/Drupal/Core/DependencyInjection/ContainerBuilder.php on line 19