--- a/web/views/basecontrollers.py	Wed Sep 30 18:03:53 2015 +0200
+++ b/web/views/basecontrollers.py	Wed Sep 30 18:04:27 2015 +0200
@@ -24,6 +24,8 @@
 
 from warnings import warn
 
+from six import text_type
+
 from logilab.common.deprecation import deprecated
 
 from cubicweb import (NoSelectableObject, ObjectNotFound, ValidationError,
@@ -233,7 +235,7 @@
     except Exception as ex:
         req.cnx.rollback()
         req.exception('unexpected error while validating form')
-        return (False, str(ex).decode('utf-8'), ctrl._edited_entity)
+        return (False, text_type(ex), ctrl._edited_entity)
     return (False, '???', None)