Fatal error: Uncaught Error: Class "Drupal\Component\Plugin\Derivative\DeriverBase" not found in /home/www/drupal8/test/core/modules/block_content/src/Plugin/Derivative/BlockContent.php:13 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/block_content/src/Plugin/Derivative/BlockContent.php on line 13