- fixes two issues identified by newer flake8
- upgrades flake8 and keeps it pinned
- removes hacking as this is no longer needed, as pre-commit does
its own pinning.
- enables us to easily add other linters, pylint would come in
follow-up
Change-Id: If26234fad0cd982bd7d3dc23c42021b357c6bde9
Related-Bug: #1910543