Fatal error: Uncaught Error: Class "Drupal\Component\Annotation\Plugin" not found in /home/www/drupal8/test/core/lib/Drupal/Core/Block/Annotation/Block.php:14 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/lib/Drupal/Core/Block/Annotation/Block.php on line 14