Fatal error: Uncaught Error: Class "Drupal\Core\Plugin\PluginBase" not found in /home/www/drupal8/test/core/lib/Drupal/Core/Field/PluginSettingsBase.php:13
Stack trace:
#0 {main}
thrown in /home/www/drupal8/test/core/lib/Drupal/Core/Field/PluginSettingsBase.php on line 13