Fatal error: Uncaught Error: Class "Drupal\rest\Plugin\ResourceBase" not found in /home/www/drupal8/test/core/modules/user/src/Plugin/rest/resource/UserRegistrationResource.php:30 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/user/src/Plugin/rest/resource/UserRegistrationResource.php on line 30