title: AttributeError when using requests.post() in `with` statement
body: <p>A/C python requests <a href="http://docs.python-requests.org/en/master/user/advanced/#advanced" rel="noreferrer">documentation</a>, with statement can be used with requests for better speed. </p>
  
  <blockquote>
    <p>with requests.get('<a href="http://httpbin.org/get" rel="noreferrer">http://httpbin.org/get</a>', stream=True) as r:
        # Do things with the response here.</p>
  </blockquote>
  
  <p>So why is this returning 'Attribute error'?</p>
  
  <pre><code>Traceback (most recent call last):
  File "&lt;pyshell#101&gt;", line 1, in &lt;module&gt;
  with requests.post(url,headers=headers,data=data,stream=True) as post_res:
  AttributeError: __exit__
  </code></pre>
  
  <p>code:</p>
  
  <pre><code>with requests.post(url,headers=headers,data=data,stream=True) as post_res:
      print(b'Name' in post_res.content)
  </code></pre>
  
  <p>P.S. This is working fine without 'with' statement.</p>