Fatal error: Uncaught Error: Class "Drupal\Tests\migrate_drupal\Kernel\d6\MigrateDrupal6TestBase" not found in /home/www/drupal8/test/core/modules/user/tests/src/Kernel/Migrate/d6/MigrateUserPictureD6FileTest.php:15 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/user/tests/src/Kernel/Migrate/d6/MigrateUserPictureD6FileTest.php on line 15