PEP8 Linting required across codebase

[tallamjr]

In order to be in-line with the style guide set out in snmachine/docs/contributing/ a codebase wide linting is required.

This is not a high-priority issue but listing here such that it can be tackled prior to public release version v2.0.0. This can even be looked into during v2.0.0-rcN stages.

[Catarina-Alves]

This is basically done at this point. There are some files that are still not fully PEP8 compliant, but these files can be updated once they are modified for some other reason.

Following this, I will remove the pre-v2.0.0 tag and leave the hack day ideas.