Issue #3114026 by longwave: simpletest_uninstall() does not work

core/modules/simpletest/simpletest.install

@@ -7,6 +7,7 @@
 
 use Drupal\Core\Database\Database;
 use Drupal\Core\File\Exception\FileException;
+use Drupal\Core\Test\EnvironmentCleaner;
 use Drupal\Core\Test\TestDatabase;
 use Symfony\Component\Console\Output\NullOutput;