Bug in rational_parameterization?

[Peter Mueller]

A slight modification of the example which documents the use of the method `rational_parameterization' yields a rather long Traceback:

A.<x,y> = AffineSpace(QQ, 2)

C = Curve([10*x^2 + 2*y^2 - 3], A)

C.rational_parameterization()

---------------------------------------------------------------------------

ValueError                                Traceback (most recent call last)

<ipython-input-1-ad1efb038e7e> in <module>()

      1 A = AffineSpace(QQ, Integer(2), names=('x', 'y',)); (x, y,) = A._first_ngens(2)

      2 C = Curve([Integer(10)*x**Integer(2) + Integer(2)*y**Integer(2) - Integer(3)], A)

----> 3 C.rational_parameterization()

SNIPPED MANY LINES

/home/sc_serv/sage/local/lib/python2.7/site-packages/sage/schemes/generic/morphism.pyc in __init__(self, parent, polys, check)

    927             target = parent._codomain.ambient_space()

    928             if len(polys) != target.ngens():

--> 929                 raise ValueError("there must be %s polynomials"%target.ngens())

    930             try:

    931                 polys = [source_ring(poly) for poly in polys]

ValueError: there must be 3 polynomials

-- Peter Müller (Würzburg)

P.S.: This happens for SageMath version 8,7 on Manjaro-Linux and at https://sagecell.sagemath.org/ too.