Put quotes around program names in some error messages
One user reported being rather confused by the message: cabal: The program happy version >=1.18.5 is required but it could not be found. I guess they must have been wondering what a happy version was. They said that this is much clearer: cabal: The program 'happy' version >=1.18.5 is required but it could not be found. So that's what we now do.