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

vendor/symfony/http-foundation/Session/Storage/Handler/NativeFileSessionHandler.php

@@ -0,0 +1,58 @@
+<?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\HttpFoundation\Session\Storage\Handler;
+
+/**
+ * NativeFileSessionHandler.
+ *
+ * Native session handler using PHP's built in file storage.
+ *
+ * @author Drak <drak@zikula.org>
+ */
+class NativeFileSessionHandler extends NativeSessionHandler
+{
+    /**
+     * Constructor.
+     *
+     * @param string $savePath Path of directory to save session files.
+     *                         Default null will leave setting as defined by PHP.
+     *                         '/path', 'N;/path', or 'N;octal-mode;/path
+     *
+     * @see http://php.net/session.configuration.php#ini.session.save-path for further details.
+     *
+     * @throws \InvalidArgumentException On invalid $savePath
+     */
+    public function __construct($savePath = null)
+    {
+        if (null === $savePath) {
+            $savePath = ini_get('session.save_path');
+        }
+
+        $baseDir = $savePath;
+
+        if ($count = substr_count($savePath, ';')) {
+            if ($count > 2) {
+                throw new \InvalidArgumentException(sprintf('Invalid argument $savePath \'%s\'', $savePath));
+            }
+
+            // characters after last ';' are the path
+            $baseDir = ltrim(strrchr($savePath, ';'), ';');
+        }
+
+        if ($baseDir && !is_dir($baseDir)) {
+            mkdir($baseDir, 0777, true);
+        }
+
+        ini_set('session.save_path', $savePath);
+        ini_set('session.save_handler', 'files');
+    }
+}