E203 erroneously flagging correctly formatted slice definition

[malikoth]

I have a line like this inside a loop in a generator:

yield collection[i : i + 10]

black insists on formatting it like that, and flake8 insists on flagging it as having improper whitespace before the colon. The pep8 discussion on whitespace shows examples of slices including spaces before the colon as acceptable conventions.

[malikoth]

Yeah, this is totally the wrong place to report this. Sorry, my bad. <3