Question: Error, (in int) wrong number (or type) of arguments: invalid options or option values passed to exact integration

Hi, I have an rational polynomial:

r:=-36*u^3*v*(-1 + u + v)*(3*u^2 + u*v - 5*u - 2*v + 2)/(-1 + u)^2;

int(r, u=0..1-v, v=0..1);

Then I got:

I'm confused, why can't maple do this?

Any ideas about how to do this exact integration?

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