Improve registration error messages

- Don't print the raw IRC message, since we already show the original
  error message
- Avoid double-printing "registration failed"

upstream.go

@@ -32,6 +32,12 @@ var permanentUpstreamCaps = map[string]bool{
 	"server-time":      true,
 }
 
+type registrationError string
+
+func (err registrationError) Error() string {
+	return fmt.Sprintf("registration error: %v", string(err))
+}
+
 type upstreamChannel struct {
 	Name         string
 	conn         *upstreamConn
@@ -1357,7 +1363,8 @@ func (uc *upstreamConn) handleMessage(msg *irc.Message) error {
 		return fmt.Errorf("fatal server error: %v", text)
 	case irc.ERR_PASSWDMISMATCH, irc.ERR_ERRONEUSNICKNAME, irc.ERR_NICKNAMEINUSE, irc.ERR_NICKCOLLISION, irc.ERR_UNAVAILRESOURCE, irc.ERR_NOPERMFORHOST, irc.ERR_YOUREBANNEDCREEP:
 		if !uc.registered {
-			return fmt.Errorf("registration failed: %v", msg.Params[len(msg.Params)-1])
+			text := msg.Params[len(msg.Params)-1]
+			return registrationError(text)
 		}
 		fallthrough
 	default:
@@ -1526,10 +1533,14 @@ func (uc *upstreamConn) runUntilRegistered() error {
 		}
 
 		if err := uc.handleMessage(msg); err != nil {
+			if _, ok := err.(registrationError); ok {
+				return err
+			} else {
 				msg.Tags = nil // prevent message tags from cluttering logs
 				return fmt.Errorf("failed to handle message %q: %v", msg, err)
 			}
 		}
+	}
 
 	for _, command := range uc.network.ConnectCommands {
 		m, err := irc.ParseMessage(command)

user.go

@@ -140,8 +140,12 @@ func (net *network) run() {
 
 		uc.register()
 		if err := uc.runUntilRegistered(); err != nil {
-			uc.logger.Printf("failed to register: %v", err)
-			net.user.events <- eventUpstreamConnectionError{net, fmt.Errorf("failed to register: %v", err)}
+			text := err.Error()
+			if regErr, ok := err.(registrationError); ok {
+				text = string(regErr)
+			}
+			uc.logger.Printf("failed to register: %v", text)
+			net.user.events <- eventUpstreamConnectionError{net, fmt.Errorf("failed to register: %v", text)}
 			uc.Close()
 			continue
 		}