Fatal error: Uncaught Error: Interface "Drupal\Core\Ajax\CommandInterface" not found in /home/www/drupal8/test/core/lib/Drupal/Core/Ajax/InvokeCommand.php:18
Stack trace:
#0 {main}
thrown in /home/www/drupal8/test/core/lib/Drupal/Core/Ajax/InvokeCommand.php on line 18