"AttributeError: url" when calling self.redirect("/") on Webapp2/Google App Engine

Question

I'm writing a small web app on AppEngine/Python for accessing the GitHub API.

I've successfully performed the Oauth2 flow (ie. I can access the logged user info). What I'd like to do now is that as the user goes back to my webpage uri which I specified as the redirect_uri for GitHub, having authorized the app, I make the request for obtaining the access token and then redirect the user to the homepage.

Now, if I perform the redirect with self.redirect("/") at the end of the handler for the redirect_uri, Python trows the error AttributeError: url.

What am I doing wrong?

Here's the class definition of the handler for redirect_uri

class RedirectGithub(webapp2.RequestHandler):
    def get(self):
        self.github_code = self.request.get("code")
        self.payload = {
        "client_id": GITHUB_CLIENT_ID, 
        "client_secret": GITHUB_CLIENT_SECRET,  
        "code": self.github_code, 
        "redirect_uri": GITHUB_REDIRECT_URI, 
    }

    self.data = urllib.urlencode(self.payload)
    self.request = urllib2.Request(GITHUB_URL_ACCESSTOKEN, self.data)
    self.github_response = urllib2.urlopen(self.request)
    github_access_token = urlparse.parse_qs(self.github_response.read())
    self.redirect("/")

Here's the full stack trace

    Traceback (most recent call last):
      File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.3/webapp2.py", line 1511, in __call__
        rv = self.handle_exception(request, response, e)
      File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.3/webapp2.py", line 1505, in __call__
        rv = self.router.dispatch(request, response)
      File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.3/webapp2.py", line 1253, in default_dispatcher
        return route.handler_adapter(request, response)
      File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.3/webapp2.py", line 1077, in __call__
        return handler.dispatch()
      File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.3/webapp2.py", line 547, in dispatch
        return self.handle_exception(e, self.app.debug)
      File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.3/webapp2.py", line 545, in dispatch
        return method(*args, **kwargs)
      File "/base/data/home/apps/MY_APP", line 125, in get
        self.redirect("/")
      File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.3/webapp2.py", line 583, in redirect
        response=self.response)
      File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.3/webapp2.py", line 1740, in redirect
        uri = str(urlparse.urljoin(request.url, uri))
      File "/base/data/home/runtimes/python27/python27_dist/lib/python2.7/urllib2.py", line 229, in __getattr__
        raise AttributeError, attr
    AttributeError: url

Answer 1

[Updated answer]

The problem comes in when the 'request' object's url is used by webapp2:

if uri.startswith(('.', '/')):
    request = request or get_request()
    uri = str(urlparse.urljoin(request.url, uri))

In this case you are overriding the RequestHandler's 'self.request' attribute with your own (to call GitHub):

self.request = urllib2.Request(GITHUB_URL_ACCESSTOKEN, self.data)

I surmise that there is no 'url' on this new request object.

I suggest that you use a different variable name, or don't store the Github request on 'self'.

=======================

[Old answer]

Going out on a limb here based on the given info, but is your handler class extending webapp2.RequestHandler? If not the url attribute may not exist in 'self'.

Please include your handler class definition and your (minimal) handler method if this is not the case.

ie:

class SomeHandler(webapp2.RequestHandler):
   ...