Ref: https://www.drupal.org/node/2208949 (D8 strategy for Drush)

rebuild.php-fire_getresponseevent.patch

diff --git a/core/rebuild.php b/core/rebuild.php
index c915aff..f26eb6f 100644
--- a/core/rebuild.php
+++ b/core/rebuild.php
@@ -15,6 +15,9 @@
 use Drupal\Core\Site\Settings;
 use Symfony\Component\HttpFoundation\Request;
 
+use Symfony\Component\HttpKernel\Event\GetResponseEvent;
+use Symfony\Component\HttpKernel\KernelEvents;
+
 // Change the directory to the Drupal root.
 chdir('..');
 
@@ -22,10 +25,15 @@
 require_once __DIR__ . '/includes/utility.inc';
 
 $request = Request::createFromGlobals();
-// Manually resemble early bootstrap of DrupalKernel::boot().
-require_once __DIR__ . '/includes/bootstrap.inc';
-DrupalKernel::bootEnvironment();
-Settings::initialize(DrupalKernel::findSitePath($request), $autoloader);
+
+$kernel = DrupalKernel::createFromRequest($request, $autoloader, 'prod');
+$kernel->boot();
+
+\Drupal::requestStack()->push($request);
+
+$httpkernel = \Drupal::service('http_kernel');
+$event = new GetResponseEvent($httpkernel, $request, $kernel::MASTER_REQUEST);
+\Drupal::service('event_dispatcher')->dispatch(KernelEvents::REQUEST, $event);
 
 if (Settings::get('rebuild_access', FALSE) ||
   ($request->get('token') && $request->get('timestamp') &&