Fatal error: Uncaught Error: Class "Drupal\Core\Entity\EntityReferenceSelection\SelectionPluginBase" not found in /home/www/drupal8/test/core/modules/views/src/Plugin/EntityReferenceSelection/ViewsSelection.php:22 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/views/src/Plugin/EntityReferenceSelection/ViewsSelection.php on line 22