I should note that a good way to find many of the more common/simple things that need changing and even to change them automatically in your plugin's python files is to use the modernize tool
https://python-modernize.readthedocs...est/index.html
or the 2to3 tool
https://docs.python.org/3/library/2to3.html
This tool however will make your files incompatible with python 2 so it should be used to detect issues only, not fix them automatically.