polytools.degree: Fixed for constant Polys. Disallow non-int numeric gen and numeric gen on multivarate expr
polytools.degree: Fixed for constant Polys. Disallow non-int numeric gen and numeric gen on multivarate expr

Fixed `degree(Poly(0, x), z)` failing with `sympy.polys.polyerrors.PolificationFailed: can't construct a polynomial from 0`
Calling `degree` with a numeric but non-integer gen is now an error: `degree(x, 1.2)` -> `sympy.polys.polyerrors.PolynomialError: a valid generator expected, got 1.2`
Calling `degree` with a multivariate expression and with an integer for `gen` is now an error: `degree(y**2+x**3, 1)` -> `ValueError: For multivariate expressions, an explicit generator must be given for gen, not an integer.`
kaushik94/sympy,kaushik94/sympy,kaushik94/sympy