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

vendor/symfony/serializer/Mapping/Loader/FileLoader.php

@@ -0,0 +1,47 @@
+<?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\Mapping\Loader;
+
+use Symfony\Component\Serializer\Exception\MappingException;
+
+/**
+ * Base class for all file based loaders.
+ *
+ * @author Kévin Dunglas <dunglas@gmail.com>
+ */
+abstract class FileLoader implements LoaderInterface
+{
+    /**
+     * @var string
+     */
+    protected $file;
+
+    /**
+     * Constructor.
+     *
+     * @param string $file The mapping file to load
+     *
+     * @throws MappingException if the mapping file does not exist or is not readable
+     */
+    public function __construct($file)
+    {
+        if (!is_file($file)) {
+            throw new MappingException(sprintf('The mapping file %s does not exist', $file));
+        }
+
+        if (!is_readable($file)) {
+            throw new MappingException(sprintf('The mapping file %s is not readable', $file));
+        }
+
+        $this->file = $file;
+    }
+}