Fatal error: Uncaught Error: Interface "Symfony\Component\Serializer\Normalizer\NormalizerInterface" not found in /home/www/drupal8/test/core/modules/serialization/src/Normalizer/CacheableNormalizerInterface.php:12 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/serialization/src/Normalizer/CacheableNormalizerInterface.php on line 12