Fatal error: Uncaught Error: Class "Drupal\serialization\Normalizer\NormalizerBase" not found in /home/www/drupal8/test/core/modules/serialization/src/Normalizer/MarkupNormalizer.php:8
Stack trace:
#0 {main}
thrown in /home/www/drupal8/test/core/modules/serialization/src/Normalizer/MarkupNormalizer.php on line 8