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

vendor/symfony/serializer/Tests/Fixtures/NormalizableTraversableDummy.php

@@ -0,0 +1,36 @@
+<?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\Serializer\Tests\Fixtures;
+
+use Symfony\Component\Serializer\Normalizer\NormalizableInterface;
+use Symfony\Component\Serializer\Normalizer\DenormalizableInterface;
+use Symfony\Component\Serializer\Normalizer\NormalizerInterface;
+use Symfony\Component\Serializer\Normalizer\DenormalizerInterface;
+
+class NormalizableTraversableDummy extends TraversableDummy implements NormalizableInterface, DenormalizableInterface
+{
+    public function normalize(NormalizerInterface $normalizer, $format = null, array $context = array())
+    {
+        return array(
+            'foo' => 'normalizedFoo',
+            'bar' => 'normalizedBar',
+        );
+    }
+
+    public function denormalize(DenormalizerInterface $denormalizer, $data, $format = null, array $context = array())
+    {
+        return array(
+            'foo' => 'denormalizedFoo',
+            'bar' => 'denormalizedBar',
+        );
+    }
+}