ui: Improve a client_migrate_info error message

client_migrate_info reports spice_server_migrate_connect() failure as
"An undefined error has occurred".  Improve to "Could not set up
display for migration".

QERR_UNDEFINED_ERROR is now unused.  Drop.

Cc: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20201113082626.2725812-6-armbru@redhat.com>

include/qapi/qmp/qerror.h

@@ -65,9 +65,6 @@
 #define QERR_REPLAY_NOT_SUPPORTED \
     "Record/replay feature is not supported for '%s'"
 
-#define QERR_UNDEFINED_ERROR \
-    "An undefined error has occurred"
-
 #define QERR_UNSUPPORTED \
     "this feature or command is not currently supported"
 

monitor/misc.c

@@ -441,7 +441,7 @@ void qmp_client_migrate_info(const char *protocol, const char *hostname,
                                     has_port ? port : -1,
                                     has_tls_port ? tls_port : -1,
                                     cert_subject)) {
-            error_setg(errp, QERR_UNDEFINED_ERROR);
+            error_setg(errp, "Could not set up display for migration");
             return;
         }
         return;