Fatal error: Uncaught Error: Interface "Drupal\Component\Render\MarkupInterface" not found in /home/www/drupal8/test/core/lib/Drupal/Core/Template/Attribute.php:65 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/lib/Drupal/Core/Template/Attribute.php on line 65