feat(library/tactic/inversion_tactic): improve error message for unknown hypothesis
feat(library/tactic/inversion_tactic): improve error message for unknown hypothesis

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