Adding linting to the CI steps

[anastasia-linzbach]

1. Adding flake8 step to CI. For now all lint errors except "Line is too long" (E501) are fixed. Current approach is to exclude this type of error.

Issue to track the remaining error - #262

Proof that lint errors block the PR:

3. Adding hook to run flake8 before commit

3. Adding test coverage config. It was already added in Test coverage config #243. But for some reason was not merged in.

4. Fixing some lint errors that accumulated

[rasavant-ms]

Looks good!
Are we planning to deprioritize fixing E501 - long line error for now?
May be add it to the backlog in that case and we can pick it up later if time permits.

[rasavant-ms]

Could we also add flake8 as a pre-commit hook so that it runs locally before commits are pushed for a PR?
This will ensure that the linter is run on code locally before it is put up for PR.

[anastasia-linzbach]

#262 Issue to track the remaining lint error