title: Twython returned a 400 (Bad Request) when tweeting an image
body: <p>I'm writing a small script in python running in Raspbian to tweet a speedtest result and i'm trying to attach the image,
  this is the code:</p>
  
  <pre><code>import sys, urllib, cStringIO
  from PIL import Image
  from twython import Twython
  
  ...
  
  file = cStringIO.StringIO(urllib.urlopen(url_img_).read())
  imagen = Image.open(file)
  print imagen
  image_ids = twitter.upload_media(media=imagen)
  print image_ids
  twitter.update_status(status=MESSAGE_, media_ids=[image_ids['media_id']])
  </code></pre>
  
  <p>but i getting this error on the <em>twitter.upload_media</em>:</p>
  
  <pre><code>Traceback (most recent call last):
    File "twitter_phy.py", line 29, in &lt;module&gt;
      image_ids = twitter.upload_media(media=imagen)
    File "/usr/local/lib/python2.7/dist-packages/twython/endpoints.py", line 140, in upload_media
      return self.post('https://upload.twitter.com/1.1/media/upload.json', params=params)
    File "/usr/local/lib/python2.7/dist-packages/twython/api.py", line 269, in post
      return self.request(endpoint, 'POST', params=params, version=version)
    File "/usr/local/lib/python2.7/dist-packages/twython/api.py", line 259, in request
      api_call=url)
    File "/usr/local/lib/python2.7/dist-packages/twython/api.py", line 198, in _request
      retry_after=response.headers.get('X-Rate-Limit-Reset'))
  twython.exceptions.TwythonError: Twitter API returned a 400 (Bad Request), media parameter is missing.
  </code></pre>
  
  <p>this is my first approach to python, please help :(</p>