# File lib/omniauth/strategy.rb, line 198
    def fail!(message_key, exception = nil)
      self.env['omniauth.error'] = exception
      self.env['omniauth.error.type'] = message_key.to_sym
      self.env['omniauth.error.strategy'] = self

      OmniAuth.config.on_failure.call(self.env)
    end