Use idna package for normalize host

[moeb1376]

Add idna package to dependencies. Remove python 2.7 from supported python versions.

[JWCook]

I like this idea, since any project dealing with URLs almost certainly already has idna as a transitive dependency (via an HTTP client or server library like requests or aiohttp).

[a-detiste]

We are removind old Python2+3 compat from Debian: future, six, unittest2, mock...

I was considering patching this one downstream because I have it on my own PC... but having this change upstream is much better :-)

Greetings

https://wiki.debian.org/Python3-six-removal