Fatal error: Uncaught Error: Class "Drupal\migrate\Plugin\MigratePluginManager" not found in /home/www/drupal8/test/core/modules/migrate/src/Plugin/MigrateSourcePluginManager.php:21 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/migrate/src/Plugin/MigrateSourcePluginManager.php on line 21