Generalize error message
As the wizard always skip those error translation, if there are changes on it,
it keep for the language the old one and the new.
It is not a big issue because the get_source will search for matching origin.
This could be fixed by changing the way error messages are defined.
We should create an Model for such message (ir.message) where the «name» will be
translatable and replace all the error message defined in the models by record
in this table. This way, we will have unambigus links: «xml id» - «db id» -
«model» «res_id».