checking code style for pull request

[methane]

In Github GUI, it's difficult to check 79 columns limitation.
How about adding pycodestyle --diff or something similar as non strict check?

[brettcannon]

This has actually come up before and Guido didn't like the idea of automated style checking. I think the only way it would be acceptable is if a simple comment was left and it wasn't a review requirement or status check (i.e. more of a suggestion).