fix for python3 incompatibility
fix for python3 incompatibility

lilleswing/deepchem,deepchem/deepchem,miaecle/deepchem,peastman/deepchem,peastman/deepchem,ktaneishi/deepchem,deepchem/deepchem,miaecle/deepchem,ktaneishi/deepchem,lilleswing/deepchem,miaecle/deepchem,ktaneishi/deepchem,lilleswing/deepchem