[code-quality] [flake8] [idea] Optional Checks in Flake8

[Ian Cordasco]

Hey all,

I was working with Joe Gordon (who's subscribed to this list) and we
realized there's a very real desire for the ability to register a
check but not have it turned on by default. Thanks to some free time
today, I've been able to throw together an example of what that would
look like in flake8: https://gitlab.com/pycqa/flake8/merge_requests/14

I'm mainly looking for community and user based feedback. Are there
objections to a feature like this? Are there pitfalls? The approach is
a bit hack-ish, granted, but I doubt this is something pep8 has any
need to absorb.

Cheers,
Ian