docs: function immutableAppHttpRedirect (url, code, cookies, headers) {
      // direct redirect to /
      if (!url) {
          url = '/'
      }
      // default to 302 redirect code
      if (!code) {
          code = 302
      }
      // create new error
      var err = new Error('Redirect')
      err.code = code
      err.cookies = cookies
      err.headers = headers
      err.url = url
      // throw error which will be handled by application framework
      throw err
  }