Cast tuple to a string, in order to use it in the mapping.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@20963 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5Type/Constraint/CategoryMembershipArity.py

@@ -95,7 +95,7 @@ class CategoryMembershipArity(Constraint):
     if not (max_arity is None and (min_arity <= arity)
         or (min_arity <= arity <= max_arity)):
       mapping = dict(base_category=base_category,
-                     portal_type=portal_type,
+                     portal_type=str(portal_type),
                      current_arity=arity,
                      min_arity=min_arity,
                      max_arity=max_arity,)