incomplet error message in validation

tiramisu/option/baseoption.py

@@ -474,7 +474,8 @@ class Option(OnlyOption):
                 # Raise ValueError if not valid
                 value = carry_out_calculation(current_opt, context=context,
                                               callback=validator,
-                                              callback_params=validator_params_)
+                                              callback_params=validator_params_,
+                                              returns_raise=True)
                 if isinstance(value, Exception):
                     return value