revert(cmake/Modules/cpplint.py): roll back to python2 version
revert(cmake/Modules/cpplint.py): roll back to python2 version

This reverts commit 65cc4d3c086187d37874526ae3d76373fa44d6d4.

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