Applying the PEP8 style guide

[Rad-hi]

This PR aims at making the majority of the code PEP8 compliant (where possible, and reasonable).

The detection of the non-compliance was done by using flake8 (python3 -m pip install flake8 && python3 -m flake8). It's to note that the changes were not done using an autoformatter to avoid unintentional changes.

The file setup.cfg was added to determine the behavior of flake8 where I introduced some custom behavior:

• max-line-length = 130 (by default, it's 79): this choice was made with the idea that 80 columns screens are a thing of the past.
• ignore:
  • E402: the find_util_path function that was introduced in PR#91 is required to be called before importing the util module. But flake8 doesn't like that because the PEP8 style guide mandates that all imports happen before any function definitions/calls (thus the special case of no-compliance).
  • E266: too many leading '#' for block comment, this has been ignored because it would require a lot of additional refactorings to be fixed, and it does not matter much (in my opinion).