Fatal error: Uncaught Error: Class "Drupal\Core\Plugin\Context\ContextDefinition" not found in /home/www/drupal8/test/core/lib/Drupal/Core/Plugin/Context/EntityContextDefinition.php:15 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/lib/Drupal/Core/Plugin/Context/EntityContextDefinition.php on line 15