Sometimes bot does not add "CLA signed" label

[ilevkivskyi]

I have noticed that last three-four days the bot did not always add the "CLA signed" label to PRs by someone who has signed the CLA. For example, this happened to me: python/typing#375

Unfortunately, I do not know how to reproduce this (could be related to #86)

[brettcannon]

I'm fairly certain it is #86 as this started to happen suddenly with no code changes to affect it.

And re-running the CLA bot on a PR is easy as adding a label like "CLA not signed" and then removing it so there's no direct harm other than someone needing to do that step.