# File lib/guard/notifiers/tmux.rb, line 41
      def available?(silent = false, options = {})
        if ENV[options.fetch(:tmux_environment, DEFAULTS[:tmux_environment])].nil?
          ::Guard::UI.error 'The :tmux notifier runs only on when Guard is executed inside of a tmux session.' unless silent
          false
        else
          true
        end
      end