code: func NewDryRun(from mail.Address, logger blog.Logger) *MailerImpl {
  	stats := metrics.NewNoopScope()
  	return &MailerImpl{
  		dialer:      dryRunClient{logger},
  		from:        from,
  		clk:         clock.Default(),
  		csprgSource: realSource{},
  		stats:       stats,
  	}
  }
docs: // New constructs a Mailer suitable for doing a dry run. It simply logs each
  // command that would have been run, at debug level.