Use black formatter

[2xyo]

Problem to Solve

Python style is not defined for this project. 😱

It's obviously not such a big deal, but there is a straightforward and easy solution to address this issue. Black.

Black is a project under the PSF umbrella. "Black reformats entire files in place. It is not configurable. It doesn't take previous formatting into account. It doesn't reformat blocks that start with # fmt: off and end with # fmt: on. # fmt: on/off have to be on the same level of indentation. It also recognizes YAPF's block comments to the same effect, as a courtesy for straddling code."

Black is used notable open-source projects: pytest, tox, Pyramid, Django, etc.

Proposed Solution

Add black to setup.py:

extras_require={  # Optional
        'dev': ['black','wheel'],
    },

(wheel for #19)

Apply black to the project:

$ black .

Add $ black --check . to the CI.

--check : Don't write the files back, just return the status. Return code 0 means nothing would change. Return code 1 means some files would be reformatted. Return code 123 means there was an internal error.

Additional Information

Doc: https://black.readthedocs.io/en/stable/

$ git clone https://github.com/OpenCTI-Platform/client-python.git 
$ cd client-python
$ black .
$ git diff --shortstat
 56 files changed, 6126 insertions(+), 4454 deletions(-)

Priority: extra low