Fatal error: Uncaught Error: Interface "Drupal\Component\Serialization\SerializationInterface" not found in /home/www/drupal8/test/core/lib/Drupal/Component/Serialization/YamlPecl.php:10 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/lib/Drupal/Component/Serialization/YamlPecl.php on line 10