Offer possibility to customise required_noti_found error message

raised by an external validator on FormBox.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@34426 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5Form/FormBox.py

@@ -143,9 +143,10 @@ class FormBoxValidator(Validator.Validator):
   """
   property_names = Validator.Validator.property_names
   message_names = Validator.Validator.message_names + \
-                  ['form_invalidated',]
+                  ['form_invalidated', 'required_not_found']
 
   form_invalidated = "Form invalidated."
+  required_not_found = 'Input is required but no input given.'
 
   def validate(self, field, key, REQUEST):
     # XXX hardcoded acquisition