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

core/scripts/db-tools.php

@@ -0,0 +1,22 @@
+#!/usr/bin/env php
+<?php
+
+use Drupal\Core\Command\DbToolsApplication;
+use Drupal\Core\DrupalKernel;
+use Drupal\Core\Site\Settings;
+use Symfony\Component\HttpFoundation\Request;
+
+if (PHP_SAPI !== 'cli') {
+  return;
+}
+
+// Bootstrap.
+$autoloader = require __DIR__ . '/../../autoload.php';
+require_once __DIR__ . '/../includes/bootstrap.inc';
+$request = Request::createFromGlobals();
+Settings::initialize(dirname(dirname(__DIR__)), DrupalKernel::findSitePath($request), $autoloader);
+$kernel = DrupalKernel::createFromRequest($request, $autoloader, 'prod')->boot();
+
+// Run the database dump command.
+$application = new DbToolsApplication();
+$application->run();