Add missing type annotation

[petere]

I noticed during unrelated work that the lint/mypy check was failing on this, so I propose this fix.

[petere]

I don't see this commit in the master branch. Was this merged correctly?

[tristan957]

Hmm this is very strange. The commit that GitHub thinks is this commit on the master branch is something completely different. Wanna just re-open a PR, and we can try this again?

[eli-schwartz]

This is a fascinating GitHub bug... @dcbaker since GitHub thinks you clicked merge on this (but I can't even be sure of that at this point) do you recall if this succeeded at any time?

[petere]

Wanna just re-open a PR, and we can try this again?

Ok, let's try that.

[petere]

Actually, this was already committed independently as 8bc8f93. So it's all done, just GitHub being a bit confused.

[eli-schwartz]

That's... definitely one way of resolving a cherry-pick by determining that the resulting patch would be empty.

[dcbaker]

I was confused since I thought I’d already fixed this, but convinced myself it was a second instance of the same issue. Very strange behavior from GitHub indeed