Computing Divisors with MAGMA

Question

I am relatively new to MAGMA, and trying to use it to verify a computation. I would like to find the ramified points of the map $\phi : C \to \mathbb{P}^1$ given by $[X:Y:Z] \mapsto [Y:Z]$, where $C$ is the curve defined by the affine equation $y^2 = x(x-1)(x-2)$. I am running into an error with the RamificationDivisor function:

> kbar := AlgebraicClosure(Rationals());
> P2<X,Y,Z> := ProjectiveSpace(kbar,2);
> P1<T,U> := ProjectiveSpace(kbar,1);
> C := Curve(P2, Y^2*Z - X*(X-Z)*(X-2*Z));
> C2 := Curve(P1);
> phi := map<C->C2|[Y,Z]>;
> D := RamificationDivisor(phi);

>> D := RamificationDivisor(phi);
                           ^
Runtime error in 'RamificationDivisor': Only implemented for maps between integral curves

I am relatively new to both MAGMA and arithmetic geometry, can someone explain the error, and whether there is a workaround?