Correct the xor operator from '-' to '^'

[astrojhgu]

Otherwise it may raise an error in python 2.7

[jakeret]

Thanks for your contribution!
Do you know what is causing the build to break?

[astrojhgu]

I don't know either. It seems the error came from the hope package, when it is trying to compile a generated c source file, which I'm not familiar.

This only thing I touch is changing '-' to '^'. So I guess it should not be caused by this modification.

(all right, I made a further modification to test_mask_objects.py, in which 01 will prevent it from accepted by python 3, so I change it to 1)

I tried to dig into it deeper, but I failed to extract the generated .c file. If it is possible, I can find out why the compilation failed.