Make the error encountered when a package can't be found more user-friendly
Make the error encountered when a package can't be found more
user-friendly

Closes #369

Helkafen/haddock,haskell/haddock,randen/haddock,lamefun/haddock,randen/haddock,lamefun/haddock,sboosali/haddock,niteria/haddock,Fuuzetsu/haddock,lamefun/haddock,esmolanka/haddock,Helkafen/haddock,randen/haddock,JPMoresmau/haddock,esmolanka/haddock,mrhania/haddock,adamse/haddock,niteria/haddock,haskell/haddock,JPMoresmau/haddock,beni55/haddock,Acidburn0zzz/haddock,Fuuzetsu/haddock,Helkafen/haddock,adamse/haddock,mrhania/haddock,beni55/haddock,haskell/haddock,niteria/haddock,Acidburn0zzz/haddock,Fuuzetsu/haddock,beni55/haddock,sboosali/haddock,mrhania/haddock,Acidburn0zzz/haddock,adamse/haddock,haskell/haddock,idontgetoutmuch/haddock,Fuuzetsu/haddock,idontgetoutmuch/haddock,JPMoresmau/haddock,idontgetoutmuch/haddock,haskell/haddock,sboosali/haddock,esmolanka/haddock