Translate Log-in-Page Ruby on rails

I created the blog application from the rails tutorial with "rails new blog".

There is a page that can only be loaded when you login with your username.

The log in page is automatically generated via rails.

I want to translate the log in page.

I changed the default_locale to :de in my application.rb. It looks like this:

...

module Blog
  class Application < Rails::Application
    config.active_record.raise_in_transactional_callbacks = true
    config.i18n.default_locale = :de
  end
end

even <%= I18n.locale %> on my index page says "de".

On the log in page ther is still "password/ Sign Up /..." in English.