Lint all Python source code

[dkav]

I have being doing this in fits and starts over the years but never actually completed the task. Most linting errors are basic and easily corrected, while some require more effort. Stubborn errors could be assigned their own issue.

Currently I use flake8, pylint and vulture. There is a pylint resource file in the repo. Line length is 79.

lm_util.py, the largest Python file, requires the most work.