# File lib/bundler/ui/shell.rb, line 33
      def warn(msg, newline = nil)
        return unless level("warn")
        return if @warning_history.include? msg
        @warning_history << msg

        return tell_err(msg, :yellow, newline) if Bundler.feature_flag.error_on_stderr?
        tell_me(msg, :yellow, newline)
      end