Issue #3251125 by Beakerboy, daffie, mondrake: Do not uninstall the database...

Issue #3251125 by Beakerboy, daffie, mondrake: Do not uninstall the database driver module within installer tests

(cherry picked from commit 4b927a02)

core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigTestBase.php

@@ -4,6 +4,7 @@
 
 use Drupal\Component\Serialization\Yaml;
 use Drupal\Core\Archiver\ArchiveTar;
+use Drupal\Core\Database\Database;
 use Drupal\Core\Installer\Form\SelectProfileForm;
 
 /**
@@ -69,6 +70,18 @@ protected function prepareEnvironment() {
       }
       $archiver->extractList($files, $config_sync_directory);
     }
+
+    // Add the module that is providing the database driver to the list of
+    // modules that can not be uninstalled in the core.extension configuration.
+    if (file_exists($config_sync_directory . '/core.extension.yml')) {
+      $core_extension = Yaml::decode(file_get_contents($config_sync_directory . '/core.extension.yml'));
+      $module = Database::getConnection()->getProvider();
+      if ($module !== 'core') {
+        $core_extension['module'][$module] = 0;
+        $core_extension['module'] = module_config_sort($core_extension['module']);
+        file_put_contents($config_sync_directory . '/core.extension.yml', Yaml::encode($core_extension));
+      }
+    }
   }
 
   /**