Run black through pre-commit

[benjaoming]

One of the design features of pre-commit is to create a separate Python environment for the linting tools. This means that Black can run outside of the development environment in some other Python version.

I would like to discuss the potential for replacing the need for this repository with "black through pre-commit", as per their official documentation. For more background on pre-commit, see the exchange here: psf/black#1073

CC: @indirectlylit @ralphiee22

[benjaoming]

This would perhaps also fix a recurring confusion: What version of Black are we even running? As per learningequality/kolibri#6004

[indirectlylit]

Yup, I tried that first. Black is limited to python 3.6+, so we were unable to use that strategy because some developers run early versions of Python 3.

ref: psf/black#585

[benjaoming]

@indirectlylit can developers not be restricted to systems with Python 3.6+? This doesn't pertain their development virtualenv since pre-commit creates its own.

The fall-back mode would be that linting is also run in CI, so a PR would still error out if the developer has skipped using pre-commit.

[benjaoming]

The pre-commit hook is specified in the official PSF repo and doesn't pin Python 3.6.. but it has to be 3.6+, I suppose. 3.5 hasn't been around for quite a while?

https://github.com/psf/black/blob/master/.pre-commit-hooks.yaml

[indirectlylit]

@indirectlylit can developers not be restricted to systems with Python 3.6+?

At the time that seemed like too much to ask, because the version of Ubuntu a few people were running came with 3.5

[benjaoming]

Let's find out :)

[indirectlylit]

Let's find out :)

That's my point - we did it this way originally and I got 2 different complaints that things were broken. Specifically, I know @rtibbles ran into this problem.

also ref: learningequality/kolibri#5409