ActiveRecord errors full_messages i18n incompatibility

If you’re running a Rails 2 app on a system with the latest i18n gem, ActiveRecord’s object.errors.full_messages spits out the string “{{attribute}} {{message}}”. You might notice that this is the old interpolation syntax for internationalisation in Rails 2. The latest i18n gem requires the %{} syntax. Sticking this into config/locales/en.yml fixed the problem for me, and future-proofs an app for when you accidentally upgrade the i18n gem on your production server: