PEP8 conformance test (with style-guide-specific exclusions)

[snark]

Basic PEP8 conformance checker with project-specific overrides (most notably around the choice of 2-space, rather than 4-space, indentation).

[snark]

Leonard, here's a PEP8 checker with the non-standard things you called out excluded from checking. I have not gone through and fixed the errors this time; I'll do that in a separate PR.

[lhl]

Sounds good, thx @snark