tox: add support for black format checker

[fjmolinas]

Added black and applied where needed.

[miri64]

Added black and applied where needed.

Can we make this a separate PR? All these extra changes make the PR harder to review.

[miri64]

Please rebase!

[fjmolinas]

Rebased and fixed PR title and description.

[fjmolinas]

All green here @miri64

[miri64]

Please squash!

[fjmolinas]

ACK. Running black . in the root dir now does not change anything.

Note that just black . would change strings, but this is skipped since is configured in tox, the equivalent would be black . --skip-string-normalization.

[miri64]

Note that just black . would change strings, but this is skipped since is configured in tox, the equivalent would be black . --skip-string-normalization.

Mhhh no, this not configured in tox, but setup.cfg. So also when you call black . in that directory ;-). setup.cfg is not just for tox ;-).

[miri64]

See

• https://docs.python.org/3/distutils/configfile.html
• https://black.readthedocs.io/en/stable/usage_and_configuration/the_basics.html#what-on-earth-is-a-pyproject-toml-file