must be a list

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@13157 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5Form/Document/Preference.py

@@ -68,7 +68,7 @@ class Preference( Folder ):
     """Clear caches used by methods of this preference
     # TODO: clear different caches according to the preference priority
     """
-    clearCache(cache_factory_list='erp5_ui_short')
+    clearCache(cache_factory_list=('erp5_ui_short'),)
 
   def _edit(self, **kw):
     """edit and clear all caches"""