Symfony 4.2 documentation :
"
For example, to override the translations defined in the Resources/translations/FOSUserBundle.es.yml file of the FOSUserBundle, create a<your-project>/translations/FOSUserBundle.es.yml
file.
"
That's doesn't work for me and i clean my cache ! Any one have some idea ? Symfony take always the FOSUserBundle.es.yml of vendor.