update isAccountable docstring.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@5981 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5/Document/InvoiceLine.py

@@ -87,9 +87,8 @@ class InvoiceLine(DeliveryLine):
                                'isAccountable' )
     def isAccountable(self):
       """
-        Returns 1 if this needs to be accounted
-        Only account movements which are not associated to a delivery
-        Whenever delivery is there, delivery has priority
+        Invoice movements are never accountable, because they have no
+        impact on stock calculations.
       """
       # Never accountable
       return 0