diff --git a/core/includes/file.inc b/core/includes/file.inc
index ee707e3439f..5c1ebde7fec 100644
--- a/core/includes/file.inc
+++ b/core/includes/file.inc
@@ -366,16 +366,15 @@ function file_stream_wrapper_uri_normalize($uri) {
  *   (Drupal\Core\StreamWrapper\PrivateStream).
  */
 function file_stream_wrapper_get_instance_by_uri($uri) {
-  $scheme = file_uri_scheme($uri);
-  $class = file_stream_wrapper_get_class($scheme);
-  if (class_exists($class)) {
-    $instance = new $class();
-    $instance->setUri($uri);
-    return $instance;
-  }
-  else {
-    return FALSE;
+  if ($scheme = file_uri_scheme($uri)) {
+    $class = file_stream_wrapper_get_class($scheme);
+    if (class_exists($class)) {
+      $instance = new $class();
+      $instance->setUri($uri);
+      return $instance;
+    }
   }
+  return FALSE;
 }
 
 /**
diff --git a/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php b/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php
index 4700203d971..0fb4e398e35 100644
--- a/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php
@@ -856,24 +856,8 @@ abstract class TestBase {
     file_prepare_directory($this->translation_files_directory, FILE_CREATE_DIRECTORY);
     $this->generatedTestFiles = FALSE;
 
-    // Create and set new configuration directories. The child site
-    // uses drupal_valid_test_ua() to adjust the config directory paths to
-    // a test-prefix-specific directory within the public files directory.
-    // @see config_get_config_directory()
-    $GLOBALS['config_directories'] = array();
-    $this->configDirectories = array();
-    include_once DRUPAL_ROOT . '/core/includes/install.inc';
-    foreach (array(CONFIG_ACTIVE_DIRECTORY, CONFIG_STAGING_DIRECTORY) as $type) {
-      // Assign the relative path to the global variable.
-      $path = 'simpletest/' . substr($this->databasePrefix, 10) . '/config_' . $type;
-      $GLOBALS['config_directories'][$type]['path'] = $path;
-      // Ensure the directory can be created and is writeable.
-      if (!install_ensure_config_directory($type)) {
-        return FALSE;
-      }
-      // Provide the already resolved path for tests.
-      $this->configDirectories[$type] = $this->originalFileDirectory . '/' . $path;
-    }
+    // Create and set new configuration directories.
+    $this->prepareConfigDirectories();
 
     // Reset and create a new service container.
     $this->container = new ContainerBuilder();
@@ -896,6 +880,32 @@ abstract class TestBase {
     $this->setupEnvironment = TRUE;
   }
 
+  /**
+   * Create and set new configuration directories.
+   *
+   * The child site uses drupal_valid_test_ua() to adjust the config directory
+   * paths to a test-prefix-specific directory within the public files
+   * directory.
+   *
+   * @see config_get_config_directory()
+   */
+  protected function prepareConfigDirectories() {
+    $GLOBALS['config_directories'] = array();
+    $this->configDirectories = array();
+    include_once DRUPAL_ROOT . '/core/includes/install.inc';
+    foreach (array(CONFIG_ACTIVE_DIRECTORY, CONFIG_STAGING_DIRECTORY) as $type) {
+      // Assign the relative path to the global variable.
+      $path = 'simpletest/' . substr($this->databasePrefix, 10) . '/config_' . $type;
+      $GLOBALS['config_directories'][$type]['path'] = $path;
+      // Ensure the directory can be created and is writeable.
+      if (!install_ensure_config_directory($type)) {
+        return FALSE;
+      }
+      // Provide the already resolved path for tests.
+      $this->configDirectories[$type] = $this->originalFileDirectory . '/' . $path;
+    }
+  }
+
   /**
    * Rebuild drupal_container().
    *
diff --git a/core/modules/system/lib/Drupal/system/Tests/Upgrade/UpgradePathTestBase.php b/core/modules/system/lib/Drupal/system/Tests/Upgrade/UpgradePathTestBase.php
index a62eb90f201..dd6703bb699 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Upgrade/UpgradePathTestBase.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Upgrade/UpgradePathTestBase.php
@@ -134,10 +134,17 @@ abstract class UpgradePathTestBase extends WebTestBase {
     $this->variable_set('site_mail', 'simpletest@example.com');
 
     drupal_set_time_limit($this->timeLimit);
-    $this->rebuildContainer();
     $this->setup = TRUE;
   }
 
+  /**
+   * Overrides \Drupal\simpletest\TestBase::prepareConfigDirectories().
+   */
+  protected function prepareConfigDirectories() {
+    // The configuration directories are prepared as part of the first access to
+    // update.php.
+  }
+
   /**
    * Specialized variable_set() that works even if the child site is not upgraded.
    *
@@ -175,7 +182,13 @@ abstract class UpgradePathTestBase extends WebTestBase {
   protected function refreshVariables() {
     // No operation if the child has not been upgraded yet.
     if (!$this->upgradedSite) {
-      return parent::refreshVariables();
+      global $conf;
+      cache('bootstrap')->delete('variables');
+      $conf = variable_initialize();
+      $container = drupal_container();
+      if ($container->has('config.factory')) {
+        $container->get('config.factory')->reset();
+      }
     }
   }
 
@@ -195,6 +208,16 @@ abstract class UpgradePathTestBase extends WebTestBase {
       throw new Exception('Initial GET to update.php did not return HTTP 200 status.');
     }
 
+    // Ensure that the first update screen appeared correctly.
+    if (!$this->assertFieldByXPath('//input[@type="submit"]')) {
+      throw new Exception('An error was encountered during the first access to update.php.');
+    }
+
+    // Initialize config directories and rebuild the service container after
+    // creating them in the first step.
+    parent::prepareConfigDirectories();
+    $this->rebuildContainer();
+
     // Continue.
     $this->drupalPost(NULL, array(), t('Continue'));
     if (!$this->assertResponse(200)) {
diff --git a/core/modules/user/user.install b/core/modules/user/user.install
index cc0bfeba666..f0b921c5020 100644
--- a/core/modules/user/user.install
+++ b/core/modules/user/user.install
@@ -949,7 +949,7 @@ function user_update_8014() {
       'module' => array(
         'description' => 'The name of the module declaring the variable.',
         'type' => 'varchar',
-        'length' => 255,
+        'length' => 204,
         'not null' => TRUE,
         'default' => '',
       ),