Make basic authentication work for python 2 & python 3

[ikarus23]

This little fix makes it possible to use droopy with basic authentication (-a) regardless of python 2/3.

[randomstuff]

It would probably be better to have a code which works with both versions without explicitly checking the Python version. I don't know

Alternatively maybe we could drop support for Python 2 ?

[ikarus23]

I would prefer dropping python 2. However, there is not much maintaining or development going on in this project. So I guess it will never happen. There are newer alternatives like https://github.com/sc0tfree/updog