Failed example:: Exception raised: Traceback (most recent call last): File "/sage/src/sage/doctest/forker.py", line 714, in _run self.compile_and_execute(example, compiler, test.globs) File "/sage/src/sage/doctest/forker.py", line 1144, in compile_and_execute exec(compiled, globs) File "<doctest sage.schemes.elliptic_curves.hom_frobenius.EllipticCurveHom_frobenius.dual[15]>", line 1, in <module> f.dual() * f == EllipticCurveHom_scalar(E, p**n) File "sage/misc/cachefunc.pyx", line 2316, in sage.misc.cachefunc.CachedMethodCallerNoArgs.__call__ self.cache = f(self._instance) File "/sage/src/sage/schemes/elliptic_curves/hom_frobenius.py", line 496, in dual Phis.append(EllipticCurveIsogeny(Ep, ker, codomain=E)) File "/sage/src/sage/schemes/elliptic_curves/ell_curve_isogeny.py", line 1072, in __init__ self.__init_from_kernel_polynomial(kernel) File "/sage/src/sage/schemes/elliptic_curves/ell_curve_isogeny.py", line 2311, in __init_from_kernel_polynomial phi, omega, v, w, _, d = self.__init_odd_kernel_polynomial(E, psi) File "/sage/src/sage/schemes/elliptic_curves/ell_curve_isogeny.py", line 2525, in __init_odd_kernel_polynomial if not is_kernel_polynomial(E, d, psi): File "/sage/src/sage/schemes/elliptic_curves/isogeny_small_degree.py", line 2406, in is_kernel_polynomial S = f.parent().quotient_ring(f) File "/sage/src/sage/categories/rings.py", line 1124, in quotient_ring return self.quotient(I, names=names, **kwds) File "/sage/src/sage/categories/rings.py", line 997, in quotient return QuotientRing(self, I, names=names, **kwds) File "/sage/src/sage/rings/quotient_ring.py", line 320, in QuotientRing return R.quotient_by_principal_ideal(I.gen(), names) File "/sage/src/sage/rings/polynomial/polynomial_ring.py", line 1846, in quotient_by_principal_ideal return PolynomialQuotientRing(self, f, names, **kwds) File "sage/structure/factory.pyx", line 373, in sage.structure.factory.UniqueFactory.__call__ return self.get_object(version, key, kwds) File "sage/structure/factory.pyx", line 410, in sage.structure.factory.UniqueFactory.get_object return self._cache[version, cache_key] File "sage/misc/weak_dict.pyx", line 707, in sage.misc.weak_dict.WeakValueDictionary.__getitem__ cdef PyObject* wr = PyDict_GetItemWithError(self, k) File "sage/rings/polynomial/polynomial_template.pxi", line 577, in sage.rings.polynomial.polynomial_zz_pex.Polynomial_template.__hash__ c_hash = hash(self[i]) File "sage/rings/polynomial/polynomial_element.pyx", line 1171, in sage.rings.polynomial.polynomial_element.Polynomial.__getitem__ return self.get_coeff_c(pyobject_to_long(n)) File "sage/rings/polynomial/polynomial_element.pyx", line 1179, in sage.rings.polynomial.polynomial_element.Polynomial.get_coeff_c return self.get_unsafe(i) File "sage/rings/polynomial/polynomial_zz_pex.pyx", line 179, in sage.rings.polynomial.polynomial_zz_pex.Polynomial_ZZ_pEX.get_unsafe return self._parent._base(ZZ_pE_c_to_list(c_pE)) File "sage/structure/parent.pyx", line 901, in sage.structure.parent.Parent.__call__ return mor._call_(x) File "sage/structure/coerce_maps.pyx", line 164, in sage.structure.coerce_maps.DefaultConvertMap_unique._call_ raise File "sage/structure/coerce_maps.pyx", line 159, in sage.structure.coerce_maps.DefaultConvertMap_unique._call_ return C._element_constructor(x) File "/sage/src/sage/categories/sets_cat.py", line 1011, in _element_constructor_from_element_class return self.element_class(self, *args, **keywords) File "sage/rings/finite_rings/element_pari_ffelt.pyx", line 338, in sage.rings.finite_rings.element_pari_ffelt.FiniteFieldElement_pari_ffelt.__init__ self.construct_from(x) File "sage/rings/finite_rings/element_pari_ffelt.pyx", line 511, in sage.rings.finite_rings.element_pari_ffelt.FiniteFieldElement_pari_ffelt.construct_from self.construct_from(self._parent.polynomial_ring()([Fp(y) for y in x])) File "sage/rings/finite_rings/element_pari_ffelt.pyx", line 495, in sage.rings.finite_rings.e