title: how to get redirect url using python requests
body: <pre><code>r = requests.get('http://techtv.mit.edu/videos/1585-music-session-02/download.source') 
  for i in r.history:
      print(i.url) 
  </code></pre>
  
  <p>I think it should print out the history, but it doesn't, the above url points to a video, but I cannot get it, anyone help? Thank you </p>