validate if import boilerplate is needed

[proppy]

In 22db071 we introduced some boilerplate to workaround namespace import differences when executing from python modules (python -m pushtotalk) vs scripts (python pushtotalk.py) for python 2.y and python 3.5.

This broke with #160 as python 3.6 changed the type of the exception raised from SystemError to ImportError.

#162 introduce a quick fix, but we should make sure to validate there is not a better way to make relative import for both cases and all supported python versions.