The enum34 module is not compatible with python3.6

[koning]

The enum34 is a backport of the enum in python3.4 and should be limited to python versions less than python3.4. In python3.6 installation of enum34 will cause an exception:
AttributeError: module 'enum' has no attribute 'IntFlag'

stackoverflow:
https://stackoverflow.com/questions/43124775/why-python-3-6-1-throws-attributeerror-module-enum-has-no-attribute-intflag

[FrankD412]

@koning -- I've made enum34 conditionally installed based on Python version, do you mind testing this to make sure it solves the issues you ran into?

[FrankD412]

Fixed by #176