Fatal error: Uncaught Error: Interface "Drupal\Component\Plugin\Context\ContextDefinitionInterface" not found in /home/www/drupal8/test/core/lib/Drupal/Core/Plugin/Context/ContextDefinitionInterface.php:13 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/lib/Drupal/Core/Plugin/Context/ContextDefinitionInterface.php on line 13