# class miadi_poidsConditionnement(models.Model):
                _sql_constraints    =    [   
                                ('uniq_id',   
                                    'UNIQUE (produit_id, conditionnement_id)',

                                    'A product already exists with this packaging !')]

Try this

check if there is any duplication before applying the constrains , if any one found then i won't take any effect , remove the duplication first then install/upgrade the module

SQL constraints works only for New Records, so you may need to test it in new Database.

Hi everybody,

I fix the problem unistalling the module and install it again