Fatal error: Uncaught Error: Class "Drupal\Core\Entity\Plugin\EntityReferenceSelection\DefaultSelection" not found in /home/www/drupal8/test/core/lib/Drupal/Core/Entity/Plugin/EntityReferenceSelection/SelectionBase.php:9 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/lib/Drupal/Core/Entity/Plugin/EntityReferenceSelection/SelectionBase.php on line 9