fix debianize on Python 3

I created few patches before uploading stdeb 0.8.2 to Debian and apparently forgot to push them upstream, sorry.

This pull request contains 2 of my patches, fix_pypi-download was already fixed and it looks like you have a different approach for pybuild (my biggest patch) so I'm not including it here. Please consider at least some changes from it

http://sources.debian.net/src/stdeb/0.8.2-3/debian/patches/