core/config/initializers/translation_missing.rb
if %w(development test).include? Rails.env
unless ENV['I18N'] == 0
module I18n
def self.just_raise_that_exception(exception, key, locale, options)
raise [exception, key].inspect if locale == 'en'
end
end
I18n.exception_handler = :just_raise_that_exception
end
end