better error message

src/risotto/dispatcher.py

@@ -1,7 +1,9 @@
 try:
     from tiramisu3 import Config
+    from tiramisu3.error import ValueOptionError
 except:
     from tiramisu import Config
+    from tiramisu.error import ValueOptionError
 from traceback import print_exc
 from copy import copy
 from typing import Dict, Callable, List, Optional
@@ -259,6 +261,8 @@ class Dispatcher(register.RegisterDispatcher,
                         if get_config()['global']['debug']:
                             print_exc()
                         raise ValueError(_(f'unknown parameter in "{uri}": "{key}"'))
+                    except ValueOptionError as err:
+                        raise ValueError(_(f'invalid parameter in "{uri}": {err}'))
                 else:
                     extra_parameters[key] = value
             # check mandatories options