Fix some doctest dataflow warnings

Author: Matthias Koeppe

src/sage/rings/generic.py

@@ -36,7 +36,7 @@ class ProductTree:
     Similarly, the :meth:`interpolation` method can be used to implement
     the inverse Fast Fourier Transform::
 
-        sage: tree.interpolation(zs).padded_list(len(ys)) == ys
+        sage: tree.interpolation(zs).padded_list(len(ys)) == ys                         # needs sage.rings.finite_rings
         True
 
     This class encodes the tree as *layers*: Layer `0` is just a tuple

src/sage/rings/polynomial/polynomial_rational_flint.pyx

@@ -2127,11 +2127,11 @@ cdef class Polynomial_rational_flint(Polynomial):
 
         ::
 
-            sage: # needs sage.libs.pari
+            sage: # needs sage.groups sage.libs.pari
             sage: f = x^4 - 17*x^3 - 2*x + 1
             sage: G = f.galois_group(pari_group=True); G
             PARI group [24, -1, 5, "S4"] of degree 4
-            sage: PermutationGroup(G)                                                   # needs sage.groups
+            sage: PermutationGroup(G)
             Transitive group number 5 of degree 4
 
         You can use KASH or GAP to compute Galois groups as well.  The advantage is

src/sage/schemes/curves/affine_curve.py

@@ -1801,6 +1801,7 @@ def fundamental_group(self, simplified=True, puiseux=False):
         to the algebraic field::
 
             sage: # needs sage.rings.number_field
+            sage: x = polygen(ZZ)
             sage: a = QQ[x](x^2 + 5).roots(QQbar)[0][0]
             sage: F = NumberField(a.minpoly(), 'a', embedding=a)
             sage: F.inject_variables()