The patch fixes only when you pass the authentication info in the proxy
handler's URL. Like:

    proxy_handler = urllib2.ProxyHandler({'https':
'http://user:pass@proxy-example.com:3128/'})

But setting the authentication using a ProxyBasicAuthHandler is still
broken:

    proxy_auth_handler = urllib2.ProxyBasicAuthHandler()
    proxy_auth_handler.add_password('realm', 'proxy-example.com:3128',
'user', 'pass')

In the attached file (urllib2_with_proxy_auth_comparison.py) we've wrote
a comparison between what works with HTTP and HTTPS.

The problem is the 407 error never reaches the ProxyBasicAuthHandler
because HTTPConnection._tunnel raises an exception when the http
response status code is not 200.