title: invalid_grant error while getting access token via OAuth 2.0
body: <p>There is a python app uses <a href="http://developer.runkeeper.com/healthgraph/getting-started" rel="nofollow">Health Graph API</a></p>
  
  <pre><code># -*- coding: utf-8 -*-
  from django.shortcuts import render_to_response, redirect
  from main.settings import CLIENT_ID, CLIENT_SECRET, RUNKEEPER_LOGIN_URL, ACCESS_TOKEN_URL
  import requests
  
  
  def index(request):
      return render_to_response('index.html')
  
  def login(request):
      code = request.GET['code']
      post_data = {'grant_type': 'authorization_code',
                   'code': code,
                   'client_id': CLIENT_ID,
                   'client_secret': CLIENT_SECRET,
                   'redirect_uri': 'http://127.0.0.1:8000/welcome/'}
  
      req = requests.post(ACCESS_TOKEN_URL, data=post_data)
  </code></pre>
  
  <p>My login button that redirects user to Health Graph Login Page and let's my app wait authorization code.</p>
  
  <pre><code>&lt;a href="https://runkeeper.com/apps/authorize?redirect_uri=http%3A%2F%2F127.0.0.1%3A8000%2Flogin&amp;response_type=code&amp;client_id=xxxxxxxxx"&gt;
  </code></pre>
  
  <p>When I try to get access token by calling login function, I getting 'invalid grant' error as request. I tried to replace 'authorization_code' to another words and I've got another 'unsupported grant type' error. Another words, token server refuses code that I getting from auth server. What I doing wrong?</p>