diff -u b/core/includes/install.core.inc b/core/includes/install.core.inc
--- b/core/includes/install.core.inc
+++ b/core/includes/install.core.inc
@@ -1193,7 +1193,7 @@
     $errors['driver'] = t("In your %settings_file file you have configured @drupal to use a %driver server, however your PHP installation currently does not support this database type.", ['%settings_file' => $settings_file, '@drupal' => drupal_install_profile_distribution_name(), '%driver' => $driver]);
   }
   else {
-    // Run driver specific validation
+    // Run driver specific validation.
     $errors += $database_types[$driver]->validateDatabaseSettings($database);
     if (!empty($errors)) {
       // No point to try further.
@@ -1914,7 +1914,7 @@
 
   $readable = FALSE;
   $writable = FALSE;
-  // @todo: Make this configurable.
+  // @todo Make this configurable.
   $site_path = \Drupal::getContainer()->getParameter('site.path');
   $files_directory = $site_path . '/files';
   $translations_directory = $site_path . '/files/translations';
diff -u b/core/includes/install.inc b/core/includes/install.inc
--- b/core/includes/install.inc
+++ b/core/includes/install.inc
@@ -946,10 +946,10 @@
   if (is_file($file)) {
     require_once $file;
   }
-  // Check requirements
+  // Check requirements.
   $requirements = \Drupal::moduleHandler()->invoke($module, 'requirements', ['install']);
   if (is_array($requirements) && drupal_requirements_severity($requirements) == REQUIREMENT_ERROR) {
-    // Print any error messages
+    // Print any error messages.
     foreach ($requirements as $requirement) {
       if (isset($requirement['severity']) && $requirement['severity'] == REQUIREMENT_ERROR) {
         $message = $requirement['description'];
diff -u b/core/lib/Drupal/Core/Messenger/Messenger.php b/core/lib/Drupal/Core/Messenger/Messenger.php
--- b/core/lib/Drupal/Core/Messenger/Messenger.php
+++ b/core/lib/Drupal/Core/Messenger/Messenger.php
@@ -112,7 +112,7 @@
    * {@inheritdoc}
    */
   public function deleteAll() {
-	  if ($this->noMessages()) {
+    if ($this->noMessages()) {
       return [];
     }
     return $this->getFlashBag()->clear();
@@ -122,7 +122,7 @@
    * {@inheritdoc}
    */
   public function deleteByType($type) {
-	  if ($this->noMessages()) {
+    if ($this->noMessages()) {
       return [];
     }
     // Flash bag gets and clears flash messages from the stack.
@@ -134,22 +134,22 @@
    */
   public function messagesByType($type) {
-	  if ($this->noMessages()) {
+    if ($this->noMessages()) {
       return [];
     }
     return $this->getFlashBag()->peek($type);
   }
 
   /**
-	 * Determines if there are no messages.
-	 *
-	 * If the session has not started and $this->messageSet there cannot be any
-	 * messages.
-	 *
-	 * @return bool
-	 *   TRUE if there are no messages, FALSE if not.
-	 */
-	protected function noMessages() {
-	  return !$this->session->isStarted() && !$this->messageSet;
-	}
+   * Determines if there are no messages.
+   *
+   * If the session has not started and $this->messageSet there cannot be any
+   * messages.
+   *
+   * @return bool
+   *   TRUE if there are no messages, FALSE if not.
+   */
+  protected function noMessages() {
+    return !$this->session->isStarted() && !$this->messageSet;
+  }
 
 }
diff -u b/core/lib/Drupal/Core/Session/SessionManager.php b/core/lib/Drupal/Core/Session/SessionManager.php
--- b/core/lib/Drupal/Core/Session/SessionManager.php
+++ b/core/lib/Drupal/Core/Session/SessionManager.php
@@ -60,7 +60,7 @@
   /**
    * The write safe session handler.
    *
-   * @todo: This reference should be removed once all database queries
+   * @todo This reference should be removed once all database queries
    *   are removed from the session manager class.
    *
    * @var \Drupal\Core\Session\WriteSafeSessionHandlerInterface
@@ -101,10 +101,10 @@
 
     $request = $this->requestStack->getCurrentRequest();
     // If a session is started prior to the the request stack having the request
-		// create one from globals.
-		if (!$request) {
-		  $request = Request::createFromGlobals();
-		}
+    // create one from globals.
+    if (!$request) {
+      $request = Request::createFromGlobals();
+    }
     $this->setOptions($this->sessionConfiguration->getOptions($request));
 
     if ($this->sessionConfiguration->hasSession($request)) {
diff -u b/core/modules/system/tests/modules/httpkernel_test/src/HttpKernel/TestMiddleware.php b/core/modules/system/tests/modules/httpkernel_test/src/HttpKernel/TestMiddleware.php
--- b/core/modules/system/tests/modules/httpkernel_test/src/HttpKernel/TestMiddleware.php
+++ b/core/modules/system/tests/modules/httpkernel_test/src/HttpKernel/TestMiddleware.php
@@ -40,6 +40,8 @@
    *   The decorated kernel.
    * @param mixed $optional_argument
    *   (optional) An optional argument.
+   * @param \Drupal\Core\Messenger\MessengerInterface $messenger
+   *   (optional) An optional argument.
    */
   public function __construct(HttpKernelInterface $kernel, $optional_argument = NULL, MessengerInterface $messenger = NULL) {
     $this->kernel = $kernel;