When extending a controller in-place (e.g. A(Controller), B(A)) and providing the exact same _cp_path as parent (no-op) execution path would go into handler for _cp_path overwriting and raise an assertion error for overwriting of existing controller. Except this is allowed (if ugly) pattern, so warn & ignore behavior (it is harmless). bzr revid: xmo@openerp.com-20130418092405-wrmmrd648b9koefu