Because of the task cancellation that can happen at any place in the
code base, it's really hard to predict in which situation a
day-divider-adjuster should have run or not, so just demote the assert
to an error. The intent is that, if we see errors with day dividers in
the future, they'll be reported along rageshakes and we'll notice this
in the logs.
Benjamin Bouvier
a21ea06bed