Small fix: use == to compare strings

[max-sixty]

is relies on interning, which is almost always OK for small strings, but reliant on language implementations

(unless there's something I'm missing about .kind?)

[shoyer]

thanks, this is definitely the right thing to do

[max-sixty]

I picked this and #2833 up b/c I have flake8 checking in my editor.

I think we moved to restricting our automated checks to pycodestyle #2642 rather than the fuller flake8. I'm generally keen on more automated checks and less reliance on humans, but defer to @shoyer as ever

[shoyer]

I think pep8speaks supports flake8 checks now, so that is a viable option. Previously it only did pycodestyle, and I didn't want to force people to read the build logs to get lint errors.