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

vendor/symfony/translation/Dumper/YamlFileDumper.php

@@ -0,0 +1,43 @@
+<?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\Translation\Dumper;
+
+use Symfony\Component\Translation\MessageCatalogue;
+use Symfony\Component\Yaml\Yaml;
+
+/**
+ * YamlFileDumper generates yaml files from a message catalogue.
+ *
+ * @author Michel Salib <michelsalib@hotmail.com>
+ */
+class YamlFileDumper extends FileDumper
+{
+    /**
+     * {@inheritdoc}
+     */
+    protected function format(MessageCatalogue $messages, $domain)
+    {
+        if (!class_exists('Symfony\Component\Yaml\Yaml')) {
+            throw new \LogicException('Dumping translations in the YAML format requires the Symfony Yaml component.');
+        }
+
+        return Yaml::dump($messages->all($domain));
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    protected function getExtension()
+    {
+        return 'yml';
+    }
+}