Fatal error: Uncaught Error: Class "Drupal\Tests\migrate\Kernel\MigrateTestBase" not found in /home/www/drupal8/test/core/modules/migrate_drupal/tests/src/Kernel/MigrateDrupalTestBase.php:11 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/migrate_drupal/tests/src/Kernel/MigrateDrupalTestBase.php on line 11