Use a dedicated error value for anonymous users.

group/group.go

@@ -22,6 +22,7 @@ var UseMDNS bool
 var UDPMin, UDPMax uint16
 
 var ErrNotAuthorised = errors.New("not authorised")
+var ErrAnonymousNotAuthorised = errors.New("anonymous users not authorised in this group")
 
 type UserError string
 
@@ -966,7 +967,7 @@ func GetDescription(name string) (*Description, error) {
 func (desc *Description) GetPermission(group string, c Challengeable) (ClientPermissions, error) {
 	var p ClientPermissions
 	if !desc.AllowAnonymous && c.Username() == "" {
-		return p, UserError("anonymous users not allowed in this group, please choose a username")
+		return p, ErrAnonymousNotAuthorised
 	}
 	if found, good := matchClient(group, c, desc.Op); found {
 		if good {

rtpconn/webclient.go

@@ -1351,6 +1351,8 @@ func handleClientMessage(c *webClient, m clientMessage) error {
 			} else if err == group.ErrNotAuthorised {
 				s = "not authorised"
 				time.Sleep(200 * time.Millisecond)
+			} else if err == group.ErrAnonymousNotAuthorised {
+				s = "please choose a username"
 			} else if e, ok := err.(group.UserError); ok {
 				s = string(e)
 			} else {