Add more linter

[PierreF]

Add black, codespell and mypy.

mypy is only partially added, mostly to client.py.

[akx]

Beyond the inline comments, I'd urge you to separate this into multiple PRs, not a single unreviewable "add more linter" one. I'm happy to review smaller PRs!

[akx]

@PierreF Note that an overarching auto-formatting PR like this will make practically every single other open PR unmergeable and nearly impossible to rebase too. Please consider merging or closing them as suitable before an auto-formatting PR (and an auto-formatting PR should only include auto-formatting).

[PierreF]

@akx thank for your feedback.

I've splitted the PR in multiple PRs:

• Add typing with mypy #791
• Add spell checking using typos #792
• Add formating #793

Closing this PR in favor of other one.

[akx]

@PierreF Thank you, and sorry if my comments sounded a bit harsh – I've just seen the maintenance pain of big PRs like this just steamrolled through 😅