Ryan Scott authored Mar 25, 2020 and Marge Bot committed Mar 31, 2020

This allows us to remove several bits of CPP that are either always
true or no longer reachable. As an added bonus, we no longer need to
worry about importing `Control.Monad.Fail.fail` qualified to avoid
clashing with `Control.Monad.fail`, since the latter is now the same
as the former.