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

vendor/symfony/dependency-injection/Tests/Fixtures/containers/container12.php

@@ -0,0 +1,12 @@
+<?php
+
+use Symfony\Component\DependencyInjection\ContainerBuilder;
+
+$container = new ContainerBuilder();
+$container->
+    register('foo', 'FooClass\\Foo')->
+    addArgument('foo<>&bar')->
+    addTag('foo"bar\\bar', array('foo' => 'foo"barřž€'))
+;
+
+return $container;