fix lingering python2 vs python3 compatibility issue
fix lingering python2 vs python3 compatibility issue

kamigaito/cnn,mitchellstern/dynet,Abasyoni/dynet,cherryc/dynet,Peilun-Li/dynet,Peilun-Li/dynet,cherryc/dynet,cherryc/dynet,Abasyoni/dynet,kamigaito/cnn,Peilun-Li/dynet,Abasyoni/dynet,mitchellstern/dynet