diff -u b/core/lib/Drupal/Core/DrupalKernel.php b/core/lib/Drupal/Core/DrupalKernel.php
--- b/core/lib/Drupal/Core/DrupalKernel.php
+++ b/core/lib/Drupal/Core/DrupalKernel.php
@@ -260,7 +260,7 @@
    */
   protected function initializeContainer() {
     $persist = array();
-    if (isset($this->container)) {
+    if (isset($this->container) && method_exists($this->container, 'findTaggedServiceIds')) {
       foreach ($this->container->findTaggedServiceIds('persist') as $id => $tags) {
         $persist[$id] = $this->container->get($id);
       }
reverted:
--- b/core/modules/system/lib/Drupal/system/Tests/System/DateFormatsLanguageTest.php
+++ a/core/modules/system/lib/Drupal/system/Tests/System/DateFormatsLanguageTest.php
@@ -100,7 +100,6 @@
     // Configure format for the node posted date changes with the language.
     $this->drupalGet('node/' . $node->nid);
     $english_date = format_date($node->created, 'custom', 'j M Y');
-    debug($english_date);
     $this->assertText($english_date, 'English date format appears');
     $this->drupalGet('fr/node/' . $node->nid);
     $french_date = format_date($node->created, 'custom', 'd.m.Y');