pre-commit hook for black should be local

[imsahil007]

While making changes for #908 #906 I noticed that we are using pre-commit hook for Black which is fetched from their Github repo.
If we want to stick to a single version of black we can use a local dependency instead in .pre-commit-config.yaml

-   repo: local
    hooks:
    -   id: black
        name: black
        description: 'Black: The uncompromising Python code formatter'
        entry: black
        language: python
        language_version: python3
        require_serial: true
        types: [python]
        additional_dependencies: ['black==19.3b0']

Though this requires running pip install black running before this.
A better option will be to create a fork for their current repo and use it for the future - which can be done by just changing the git remote to the new one .pre-commit-config.yaml.
They have not updated the documentation about this. But you can read more about this here

[terriko]

Thanks so much for digging in to this. It's kind of surprising that we haven't had more black compatibility questions before this!

[imsahil007]

Thanks so much for digging in to this. It's kind of surprising that we haven't had more black compatibility questions before this!

You're welcome!
I think it will be much better if use a particular Python package from https://pypi.org/project/black/ or create a fork of their current repo. This way our black tests won't fail. We can timely update the pre-hook to the stable version by rebasing the fork. And if we just use pip install black we will always point to the stable version from Pypi