quasicomputational authored Jun 27, 2018 and Alexis Williams committed Jul 09, 2018

This also significantly improves the error when trying to refer to
missing directories, hopefully making it clear that it's coming from
Cabal. #5318 and snowleopard/hadrian#634 are two bugs which manifested
as Cabal trying to glob in a non-existent directory and both took some
debugging because of the obscurity of the error.