Trac 15801: reinstated test in vector spaces after some mess up in th…

…e #10963 branch; updated some doctests

src/sage/categories/modules.py

@@ -49,9 +49,9 @@ class Modules(Category_module):
         Category of vector spaces over Rational Field
 
         sage: Modules(Rings())
-        Category of modules over Category of rings
+        Category of modules over rings
         sage: Modules(FiniteFields())
-        Category of vector spaces over Category of finite fields
+        Category of vector spaces over finite fields
 
         sage: Modules(Integers(9))
         Category of modules over Ring of integers modulo 9

src/sage/categories/vector_spaces.py

@@ -49,7 +49,7 @@ def __classcall_private__(cls, K, check=True):
             sage: VectorSpaces(ZZ)
             Traceback (most recent call last):
             ...
-            AssertionError: The base ring must be a field.
+            ValueError: base must be a field or a subcategory of Fields(); got Integer Ring
 
         With ``check=False``, the check is disabled, possibly enabling
         incorrect inputs::
@@ -58,7 +58,9 @@ def __classcall_private__(cls, K, check=True):
             Category of vector spaces over Integer Ring
         """
         if check:
-            assert K in _Fields, "The base ring must be a field."
+            if not (K in _Fields or
+                    isinstance(K, Category) and K.is_subcategory(_Fields)):
+                raise ValueError, "base must be a field or a subcategory of Fields(); got %s"%K
         return super(VectorSpaces, cls).__classcall__(cls, K)
 
     def __init__(self, K):
@@ -70,7 +72,7 @@ def __init__(self, K):
             sage: VectorSpaces(ZZ)
             Traceback (most recent call last):
             ...
-            AssertionError: The base ring must be a field.
+            ValueError: base must be a field or a subcategory of Fields(); got Integer Ring
 
         TESTS::
 

src/sage/rings/polynomial/polynomial_ring.py

@@ -257,9 +257,9 @@ def __init__(self, base_ring, name=None, sparse=False, element_class=None, categ
             x^3 - 26/3*x^2 + 64/3*x - 32/3
 
             sage: category(ZZ['x'])
-            Join of Category of unique factorization domains and Category of commutative algebras over Category of euclidean domains
+            Join of Category of unique factorization domains and Category of commutative algebras over euclidean domains
             sage: category(GF(7)['x'])
-            Join of Category of euclidean domains and Category of commutative algebras over Join of Category of finite fields and Category of subquotients of monoids and Category of quotients of semigroups
+            Join of Category of euclidean domains and Category of commutative algebras over (finite fields and subquotients of monoids and quotients of semigroups)
         """
         # We trust that, if category is given, it is useful and does not need to be joined
         # with the default category