The issue http://bugs.python.org/issue21224 is about http server implementations. The issue http://bugs.python.org/issue9740 is more relevant for what I talking about, but not exactly.

Look, in this line 

https://hg.python.org/cpython/file/6a2f74811240/Lib/http/client.py#l786

http protocol version is setted and in this line 

https://hg.python.org/cpython/file/6a2f74811240/Lib/http/client.py#l1036

variable used to send http method (GET, PUT etc) and it work for direct connection or proxy with http connections. But if required to use CONNECT method through proxy (usually used for https connection) will be used _tunnel() method from http.client (py3k) or httplib (py2.7)

https://hg.python.org/cpython/file/6a2f74811240/Lib/http/client.py#l871

and here version off http is hardcoded to HTTP/1.0

PIP use urllib3, but urllib3 for actual network working (work with socket and send request) use httplib or http.client. So I think it would be better to make changes in httplib than override _tunnel() method in urllib3.

P.S. I'm not sure about rules how to open/close issues, so I open this issue again. I'm sorry if this causes some inconvenience.