Fatal error: Uncaught Error: Interface "Drupal\Component\Plugin\ConfigurablePluginInterface" not found in /home/www/drupal8/test/core/lib/Drupal/Core/Block/BlockPluginInterface.php:23 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/lib/Drupal/Core/Block/BlockPluginInterface.php on line 23