py bindings -- fix another minor bug caught from test suite
py bindings -- fix another minor bug caught from test suite


Former-commit-id: 77871d653b3471c82015cdef430058c8e485eb25
Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide