When using Symfony's form_login feature with the ezpublish user provider, the following exception is displayed when attempting to login with valid user credentials:

"Argument 'userId' is invalid: *username* is wrong value"

Using, for example, an in_memory user provider, works as expected.

Ref: http://symfony.com/doc/current/book/security.html#using-a-traditional-login-form

Steps to reproduce:

1 - Setup a login form using the Security component, as documented in the link above, and using the (configured by default) ezpublish user provider.
2 - Attempt to login using the login form with valid credentials