Fatal error: Uncaught Error: Class "Drupal\webform\Plugin\WebformExporterBase" not found in /home/www/drupal8/test/modules/webform/src/Plugin/WebformExporter/TabularBaseWebformExporter.php:11 Stack trace: #0 {main} thrown in /home/www/drupal8/test/modules/webform/src/Plugin/WebformExporter/TabularBaseWebformExporter.php on line 11