In emacsclient, if an existing Emacs server cannot be found and an alternate editor is specified, the alternate editor is started. Along the way, emacsclient generates a warning that the server cannot be found.
On Windows, this warning is a pop-up dialog box that must be dismissed by the user. This is an unwanted interruption, and irrelevant, since the user has already indicated by using the --alternated-editor option how to handle this situation.
The patch below suppresses this warning when the user has specified both the --quiet option and the --alternate-editor option. The reasoning is that --quiet mutes all messages on success, and that because the --alternate-editor has been specified, this message is not reporting an error. It seems like a reasonable compromise that will allow users to see this warning if they like (by not using --quiet) and allow users to avoid it if they like (by using --quiet).