Fatal error: Uncaught Error: Interface "Drupal\Core\Render\Placeholder\PlaceholderStrategyInterface" not found in /home/www/drupal8/test/core/modules/big_pipe/src/Render/Placeholder/BigPipeStrategy.php:61 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/big_pipe/src/Render/Placeholder/BigPipeStrategy.php on line 61