feat(library/module): expand 'failed to import' error message
feat(library/module): expand 'failed to import' error message

see issue #448

fpvandoorn/lean,javra/lean,javra/lean,avigad/lean,sp3ctum/lean,eigengrau/lean,UlrikBuchholtz/lean,htzh/lean,fgdorais/lean,soonhokong/lean-windows,c-cube/lean,eigengrau/lean,UlrikBuchholtz/lean,rlewis1988/lean,sp3ctum/lean,Kha/lean,levnach/lean,leanprover/lean,fpvandoorn/lean,soonhokong/lean-windows,fgdorais/lean,avigad/lean,Kha/lean,leodemoura/lean,fgdorais/lean,soonhokong/lean,fpvandoorn/lean,johoelzl/lean,dselsam/lean,sp3ctum/lean,leanprover/lean,fpvandoorn/lean2,dselsam/lean,avigad/lean,levnach/lean,dselsam/lean,UlrikBuchholtz/lean,c-cube/lean,rlewis1988/lean,leodemoura/lean,digama0/lean,fgdorais/lean,c-cube/lean,javra/lean,leodemoura/lean,fpvandoorn/lean2,soonhokong/lean-windows,leanprover/lean,eigengrau/lean,fpvandoorn/lean,rlewis1988/lean,dselsam/lean,levnach/lean,c-cube/lean,leodemoura/lean,fgdorais/lean,javra/lean,digama0/lean,soonhokong/lean,fpvandoorn/lean2,digama0/lean,dselsam/lean,htzh/lean,avigad/lean,johoelzl/lean,soonhokong/lean-osx,dselsam/lean,levnach/lean,johoelzl/lean,soonhokong/lean-osx,leanprover-community/lean,avigad/lean,leanprover/lean,sp3ctum/lean,Kha/lean,leanprover/lean,Kha/lean,leanprover-community/lean,htzh/lean,soonhokong/lean-windows,leanprover/lean,fpvandoorn/lean,levnach/lean,Kha/lean,soonhokong/lean-windows,sp3ctum/lean,fpvandoorn/lean2,leanprover-community/lean,fpvandoorn/lean2,johoelzl/lean,leodemoura/lean,Kha/lean,digama0/lean,c-cube/lean,rlewis1988/lean,leanprover-community/lean,soonhokong/lean,leanprover-community/lean,johoelzl/lean,rlewis1988/lean,avigad/lean,soonhokong/lean-osx,rlewis1988/lean,leanprover-community/lean,UlrikBuchholtz/lean,soonhokong/lean,fgdorais/lean,johoelzl/lean,digama0/lean,htzh/lean,UlrikBuchholtz/lean,digama0/lean,eigengrau/lean,htzh/lean,soonhokong/lean-osx,soonhokong/lean-osx,eigengrau/lean,leodemoura/lean,javra/lean,soonhokong/lean,fpvandoorn/lean