fix issues caught by flake8 and add CI job to run linter
Adds job to run flake8 against the sources to catch PEP 8 violations and other coding errors.
Fixed all issues already caught by flake8 (minus a few that have been explicitly ignored).
Adds job to run flake8 against the sources to catch PEP 8 violations and other coding errors.
Fixed all issues already caught by flake8 (minus a few that have been explicitly ignored).