CONTRIBUTING files are referencing nox --session=black

The two CONTRIBUTING.rst file in this repo are refferencing the command `nox --session=black``

This session name doesn’t exist in any noxfile.py in the repo. The documentation needs update.

[oncleben31]

OK we are aligned. I will work on the PR soon.

[cjolowicz]

Oh, I just realized that you’re right: the generated project does not have any information about how to install the pre-commit hook. This information is only present in the User Guide of the Cookiecutter template, which is not linked anywhere from the generated project.

So then yes 💯 ! Please do add a short note to the Contributor Guide ({{cookiecutter.project_name}}/CONTRIBUTING.rst}}). I would suggest to add something like the following instead of the note about nox --session=black:

Install pre-commit as a Git hook by running the following command:

.. code:: console

   $ nox --session=pre-commit -- install