21391: doctest fixes

src/sage/libs/pynac/pynac.pyx

@@ -809,8 +809,13 @@ cdef int py_get_parent_char(o) except -1:
         sage: p = next_prime(2^100)
         sage: R.<y> = FiniteField(p)[]
         sage: y = SR(y)
+        Traceback (most recent call last):
+        ...
+        TypeError: Multiplication of symbolic variable and an element of a ring with positive characteristic.
         sage: x + y
-        x + y
+        Traceback (most recent call last):
+        ...
+        TypeError: unsupported operand parent(s) for +: ...
         sage: p * y
         0
     """

src/sage/rings/polynomial/laurent_polynomial.pyx

@@ -573,14 +573,13 @@ cdef class LaurentPolynomial_univariate(LaurentPolynomial_generic):
             sage: g(x=2)
             9
 
-        The polynomial does not have to be over a field of
-        characteristic 0::
+        The polynomial must be over a field of characteristic 0::
 
             sage: R.<w> = LaurentPolynomialRing(GF(7))
             sage: f = SR(2*w^3 + 1); f
-            2*w^3 + 1
-            sage: f.variables()
-            (w,)
+            Traceback (most recent call last):
+            ...
+            TypeError: Multiplication of symbolic variable and an element of a ring with positive characteristic.
         """
         d = dict([(repr(g), R.var(g)) for g in self.parent().gens()])
         return self.subs(**d)

src/sage/rings/polynomial/polynomial_element.pyx

@@ -1269,14 +1269,13 @@ cdef class Polynomial(CommutativeAlgebraElement):
             sage: g(x=2)
             10
 
-        The polynomial does not have to be over a field of
-        characteristic 0::
+        The polynomial must be over a field of characteristic 0::
 
             sage: R.<w> = GF(7)[]
             sage: f = SR(2*w^3 + 1); f
-            2*w^3 + 1
-            sage: f.variables()
-            (w,)
+            Traceback (most recent call last):
+            ...
+            TypeError: Multiplication of symbolic variable and an element of a ring with positive characteristic.
         """
         d = dict([(repr(g), R.var(g)) for g in self.parent().gens()])
         return self.subs(**d)

src/sage/rings/polynomial/polynomial_zz_pex.pyx

@@ -237,7 +237,9 @@ cdef class Polynomial_ZZ_pEX(Polynomial_template):
             sage: P.<y> = F[]
             sage: p = y^4 + x*y^3 + y^2 + (x + 1)*y + x + 1
             sage: SR(p)      #indirect doctest
-            y^4 + x*y^3 + y^2 + (x + 1)*y + x + 1
+            Traceback (most recent call last):
+            ...
+            TypeError: Multiplication of symbolic variable and an element of a ring with positive characteristic.
             sage: p(2)
             x + 1
             sage: p(y=2)