Functionality reduction? How to customize full_message for validation error using i18n in Rails 3?

Folks,

I just posted a bug report about this:
https://rails.lighthouseapp.com/projects/8994-ruby-on-rails/tickets/6274-ability-to-specify-a-custom-translation-for-full_messages-gone-in-rails-3x

The more I think about this, the more puzzled I am as to what the new
convention for Rails 3 is to override a validation error that doesn't
fit into the "%{attribute} %{message}" format that the current
framework imposes.

In Rails 2.3, it was possible to override the :full_message on a per-
attribute basis through i18N, in em.yml. I can't find any
documentation or even discussion about it. The only vague reference is
a thread from a year ago by Rodrigo Rosenfeld Rosas to override the
full_message as a validation parameter, but that didn't fly either.

Concretely, given code like this:

errors.add(:credit_card_number, :authentication_failure)

I want to be able to have a custom message that doesn't start with the
attribute name. I do want to add the error to the attribute, however,
so that the correct form field gets highlighted. I'd be most grateful
if anyone could point me in the right direction, if I overlooked
something, or confirm that this was removed from Rails 2.3.x

Thanks,

Wolf

How about this approach?

https://rails.lighthouseapp.com/projects/8994/tickets/3768-patch-add-full_message-option-to-validations

Rodrigo.