make checkformat fails with missing flake8 in fresh checkout.

[jorge-leon]

Describe the bug

make checkformat complains about missing flake8, if following the README instructions.

This can be fixed manually with pip install flake8 but should rather be fixed in requirements-dev.txt.

Expected behavior

make checkformat should succeed on a fresh checkout.

Screenshots

Additional context

The current source yields about 85 warnings. Is correct formatting still a goal for the project?