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

vendor/symfony/dependency-injection/Extension/PrependExtensionInterface.php

@@ -0,0 +1,24 @@
+<?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\DependencyInjection\Extension;
+
+use Symfony\Component\DependencyInjection\ContainerBuilder;
+
+interface PrependExtensionInterface
+{
+    /**
+     * Allow an extension to prepend the extension configurations.
+     *
+     * @param ContainerBuilder $container
+     */
+    public function prepend(ContainerBuilder $container);
+}