Avoid using double callable objects for caching. Use a decorator instead (but...

Avoid using double callable objects for caching. Use a decorator instead (but not with the decorator syntax for portability).

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@17354 20353a03-c40f-0410-a6d1-a30d3c3de9de