diff -u b/core/lib/Drupal/Core/Config/FileStorage.php b/core/lib/Drupal/Core/Config/FileStorage.php
--- b/core/lib/Drupal/Core/Config/FileStorage.php
+++ b/core/lib/Drupal/Core/Config/FileStorage.php
@@ -105,6 +105,7 @@
    */
   public function read() {
     if (!$this->exists()) {
+      // Use var_export to quote $this->name to separate from text.
       throw new FileStorageReadException('Configuration file ' . var_export($this->name, TRUE) . ' does not exist.');
     }
 
reverted:
--- b/core/modules/block/block.test
+++ a/core/modules/block/block.test
@@ -166,7 +166,7 @@
   function testBlockVisibility() {
     // Enable Node module and change the front page path to 'node'.
     module_enable(array('node'));
+    variable_set('site_frontpage', 'node');
-    config('system.site')->set('page.front', 'node')->save();
 
     $block = array();
 
only in patch2:
unchanged:
--- a/core/modules/block/lib/Drupal/block/Tests/BlockTest.php
+++ b/core/modules/block/lib/Drupal/block/Tests/BlockTest.php
@@ -167,7 +167,7 @@ class BlockTest extends WebTestBase {
   function testBlockVisibility() {
     // Enable Node module and change the front page path to 'node'.
     module_enable(array('node'));
-    variable_set('site_frontpage', 'node');
+    config('system.site')->set('page.front', 'node')->save();
 
     $block = array();