Unrecognized option "resource" under "fos_user"

move the :

fos_user:
    resource: "@FOSUserBundle/Resources/config/routing/all.xml" 

into config/routes.yaml insted of confing/packages/routing.yml

Dlondero's suggestion fixed the issue, the fos_user configuration should be set in config/routes.yaml.

From documentation, routes are never automatically added in configuration.