Fatal error: Uncaught Error: Class "Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem" not found in /home/www/drupal8/test/core/modules/entity_reference/src/ConfigurableEntityReferenceItem.php:15 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/entity_reference/src/ConfigurableEntityReferenceItem.php on line 15