Fatal error: Uncaught Error: Class "Drupal\Core\Display\VariantBase" not found in /home/www/drupal8/test/core/modules/block/src/Plugin/DisplayVariant/BlockPageVariant.php:32 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/block/src/Plugin/DisplayVariant/BlockPageVariant.php on line 32