Fatal error: Uncaught Error: Interface "Drupal\Core\TypedData\ComplexDataInterface" not found in /home/www/drupal8/test/core/lib/Drupal/Core/Field/FieldItemInterface.php:21 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/lib/Drupal/Core/Field/FieldItemInterface.php on line 21