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


Former-commit-id: e6ab58b9026de149ae850fc41633cb95931db626
clab/cnn,chunyang-wen/dynet,xunzhang/dynet,shuheik/dynet,clab/dynet,clab/cnn,danielhers/dynet,xunzhang/dynet,xunzhang/dynet,clab/dynet,xunzhang/dynet,chunyang-wen/dynet,shuheik/dynet,clab/dynet,danielhers/dynet,chunyang-wen/dynet,danielhers/dynet,shuheik/dynet,shuheik/dynet,shuheik/dynet,chunyang-wen/dynet,clab/dynet,danielhers/dynet,danielhers/dynet,clab/dynet,clab/cnn,clab/dynet,danielhers/dynet,clab/dynet,shuheik/dynet,shuheik/dynet,danielhers/dynet