Fix issues found by flake8-bugbear:
* Unused loop variables
* assert statements in non-test code
* mixing test code with production code
* mark one excessive test which takes ~10min to run
as 'slow'
16:Bug
“If you elect to see all the pictures, this program has the ability of consuming well over six feet of terminal paper per run. We can only suggest recycling the paper by using the other side.”