Fatal error: Uncaught Error: Class "Drupal\Component\Annotation\Plugin" not found in /home/www/drupal8/test/core/lib/Drupal/Core/Field/Annotation/FieldWidget.php:22 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/lib/Drupal/Core/Field/Annotation/FieldWidget.php on line 22