title: Error getting json using oauthlib python
body: <p>Im trying to get a pretty json but always have the same error <code>expected string or buffer</code> my code is below</p>
  
  <pre><code>        import urllib2
          import json
          import logging
          from libs.requests_oauthlib import OAuth1Session
          import libs.requests2
  
          coke = OAuth1Session('user_key',
                               client_secret='user_secret',
                               resource_owner_key='key',
                               resource_owner_secret='key_secret')
  
          headers = {'content-type': 'application/json'}
          url = "http://test.hdp.pengostores.mx/api/rest/orders"
  
  
          response = coke.get(url,headers=headers)
          self.response.out.write(response.text)
  </code></pre>
  
  <p>My log:</p>
  
  <pre><code>&lt;type 'exceptions.Exception'&gt; (/base/data/home/apps/s~precise-line-76299minutos/devvic.398776853921596377/delivery/handlers.py:5278)
  Traceback (most recent call last):
    File "/base/data/home/apps/s~precise-line-76299minutos/devvic.398776853921596377/delivery/handlers.py", line 5274, in get
      response = json.loads(coke.get(url,headers=headers))
    File "/base/data/home/runtimes/python27/python27_dist/lib/python2.7/json/__init__.py", line 338, in loads
      return _default_decoder.decode(s)
    File "/base/data/home/runtimes/python27/python27_dist/lib/python2.7/json/decoder.py", line 365, in decode
      obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  TypeError: expected string or buffer
  </code></pre>