Starting with 5240116f3c we only support
GHC versions 8.4.4 and up (more precisely, the GHC version associated
with stackage lts-12 and up). The imports in question are now in
Prelude and need not be imported explicitly.
This change needs base-4.9.0.0 or later so that we can
include Control.Monad.Fail. We could jump through hoops to
support older compilers still, but it feels like it's not
worthwhile.