Update to drupal 8.0.0-rc1. For more information, see https://www.drupal.org/node/2582663

vendor/symfony/http-kernel/Tests/Fixtures/TestClient.php

@@ -0,0 +1,31 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\HttpKernel\Tests\Fixtures;
+
+use Symfony\Component\HttpKernel\Client;
+
+class TestClient extends Client
+{
+    protected function getScript($request)
+    {
+        $script = parent::getScript($request);
+
+        $autoload = file_exists(__DIR__.'/../../vendor/autoload.php')
+            ? __DIR__.'/../../vendor/autoload.php'
+            : __DIR__.'/../../../../../../vendor/autoload.php'
+        ;
+
+        $script = preg_replace('/(\->register\(\);)/', "$0\nrequire_once '$autoload';\n", $script);
+
+        return $script;
+    }
+}