Since we've recently added German to the available languages, and we
might support every language in the future, we're using the fictional
world language to check a locale which isn't available.
Another option could be to set the available locales in the test
environment (or the rspec helper), but then we'd have to make sure it's
executed before the call to `globalize_accessors` in the model, and it
might be confusing for developers.
In order to be consistent with similar specs, the I18nContent#begins_with_key
spec was improved by explicitly specifying an I18n key for one (1) factory
that relied on its default value
