imprv: Startup: Show hint in console if Gajim is already running

Fixes #11039

gajim/gtk/application.py

@@ -383,6 +383,8 @@ def _handle_local_options(self,
 
         self.register()
         if self.get_is_remote():
+            print('Gajim is already running. '
+                  'The primary instance will handle remote commands')
             return -1
 
         self._core_command_line(options)