Fatal error: Uncaught Error: Class "Drupal\block\Plugin\DisplayVariant\BlockPageVariant" not found in /home/www/drupal8/test/core/modules/block_place/src/Plugin/DisplayVariant/PlaceBlockPageVariant.php:22 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/block_place/src/Plugin/DisplayVariant/PlaceBlockPageVariant.php on line 22