title: How to pass proxy-authentication (requires digest auth) by using python requests module
body: <p>I was using Mechanize module a while ago, and now try to use Requests module. <br>
  (<a href="https://stackoverflow.com/questions/13505349/">Python mechanize doesn&#39;t work when HTTPS and Proxy Authentication required</a>)</p>
  
  <p>I have to go through proxy-server when I access the Internet. <br>
  The proxy-server requires authentication. I wrote the following codes.</p>
  
  <pre><code>import requests
  from requests.auth import HTTPProxyAuth
  
  proxies = {"http":"192.168.20.130:8080"}
  auth = HTTPProxyAuth("username", "password")
  
  r = requests.get("http://www.google.co.jp/", proxies=proxies, auth=auth)
  </code></pre>
  
  <p>The above codes work well when proxy-server requires basic authentication. <br>
  Now I want to know what I have to do when proxy-server requires digest authentication. <br>
  HTTPProxyAuth seems not to be effective in digest authentication (r.status_code returns 407). </p>