Bug report

Bug summary

There should be a way to use different config files for different python versions, or at least specify different backends for different versions. I have PyQt5 installed for python3, so I prefer to set my backend to Qt5Agg. But occasionally I want to run something in python2 for testing or compatibility purposes. I don't want to waste time and space installing PyQt5 on python2, so I want the backend to stay TkAgg. A workaround is to change the config files in the matplotlib installation, but these will be overwritten on the next install.