Remove last vestiges of ['q'] from the kernel branch.

core/lib/Drupal/Core/EventSubscriber/PathSubscriber.php

@@ -24,9 +24,6 @@ class PathSubscriber implements EventSubscriberInterface {
    * @todo The path system should be objectified to remove the function calls
    * in this method.
    *
-   * @todo We're writing back to $_GET['q'] for temporary BC. All instances of
-   * $_GET['q'] should be removed and then this code eliminated.
-   *
    * @param GetResponseEvent $event
    *   The Event to process.
    */

core/lib/Drupal/Core/ExceptionController.php

@@ -294,7 +294,7 @@ protected function getLastCaller($backtrace) {
    *   The Event to process.
    */
   public function on404Html(FlattenException $exception, Request $request) {
-    watchdog('page not found', check_plain($_GET['q']), NULL, WATCHDOG_WARNING);
+    watchdog('page not found', check_plain($request->attributes->get('system_path')), NULL, WATCHDOG_WARNING);
 
     // Check for and return a fast 404 page if configured.
     // @todo Inline this rather than using a function.