Example code to show that localhost:8888/test redirects to localhost:8888/ after authentication.

redirect_uri.py

#! /usr/bin/env python
import datetime
import tornado.auth
import tornado.httpserver
import tornado.web

class LoginHandler(tornado.web.RequestHandler):
    def get_current_user(self):
        return self.get_secure_cookie("user")

class AuthHandler(LoginHandler, tornado.auth.GoogleMixin):
    @tornado.web.asynchronous
    def get(self):
        if self.get_argument('openid.mode', None):
            self.get_authenticated_user(self.async_callback(self._on_auth))
        else:
            self.authenticate_redirect()

    def _on_auth(self, user):
        if not user:
            raise tornado.web.HTTPError(500, "Google auth failed")
        expires = datetime.datetime.utcnow() + datetime.timedelta(minutes=90)
        self.set_secure_cookie("user", user['email'], expires=expires) 
        self.redirect(self.get_argument('next', '/'))

class TestHandler(LoginHandler):
    @tornado.web.authenticated
    def get(self):
        self.clear()
        self.write('Test')
        self.finish()

class RootHandler(tornado.web.RequestHandler):
    def get(self):
        self.clear()
        self.write('Root')
        self.finish()

class Application(tornado.web.Application):
    def __init__(self):
        handlers = [
            (r'/', RootHandler),
            (r'/test', TestHandler),
            (r'/auth/login', AuthHandler)
        ]
        settings = dict(
            cookie_secret='blablabla',
            xsrf_cookies=True,
            login_url='/auth/login',
            debug=True
        )
        tornado.web.Application.__init__(self, handlers, **settings)

def main():
    http_server = tornado.httpserver.HTTPServer(Application())
    http_server.listen(8888)
    tornado.ioloop.IOLoop.instance().start()

if __name__ == '__main__':
    main()