Looks to me as if `format_message` shouldn't be here at all. My guess is that `structure_message` has replaced `format_message`. As a result I think that this line should become `Hiera.warn message` otherwise we'd simply get a new error about a missing `format_message`. Do you have some time to confirm @andrewh? If not, I'll try to pick it up.

This seems to be backed up by dabdcdc8284ff52b61b75f370d6a0ebda3dcb394 where the first bit of this change took shape.