Issue #1847828 by chx: Fixed testbot failures.

core/modules/simpletest/lib/Drupal/simpletest/DrupalUnitTestBase.php

@@ -64,13 +64,6 @@ abstract class DrupalUnitTestBase extends UnitTestBase {
   private $themeFiles;
   private $themeData;
 
-  /**
-   * Base service container for rebooting DrupalKernel.
-   *
-   * @var \Drupal\Core\DependencyInjection\ContainerBuilder
-   */
-  private $baseContainer;
-
   /**
    * Sets up Drupal unit test environment.
    *
@@ -125,6 +118,8 @@ protected function setUp() {
    */
   public function containerBuild($container) {
     global $conf;
+    // Keep the container object around for tests.
+    $this->container = $container;
     $conf['lock_backend'] = 'Drupal\Core\Lock\NullLockBackend';
     $conf['cache_classes'] = array('cache' => 'Drupal\Core\Cache\MemoryBackend');
     $container