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

vendor/symfony/routing/Tests/Fixtures/validpattern.php

@@ -0,0 +1,18 @@
+<?php
+
+use Symfony\Component\Routing\RouteCollection;
+use Symfony\Component\Routing\Route;
+
+$collection = new RouteCollection();
+$collection->add('blog_show', new Route(
+    '/blog/{slug}',
+    array('_controller' => 'MyBlogBundle:Blog:show'),
+    array('locale' => '\w+'),
+    array('compiler_class' => 'RouteCompiler'),
+    '{locale}.example.com',
+    array('https'),
+    array('GET', 'POST', 'put', 'OpTiOnS'),
+    'context.getMethod() == "GET"'
+));
+
+return $collection;