Some checks happen while trying to merge, making react-to-comments slightly unreliable

[bnjbvr]

See for instance this (sorry about link to internal repo), where a PR is passing all the checks, so octobors will try to merge the PR, but it aborts because some of the Github checks (in this case, all comments must be closed first) aren't passing yet.

It would be nice if all the checks would happen before the attempt to merge happens, so the comment posted by the bot is more realistic.