It appears there's no builtin way for WeeChat to issue a terminal bell
 on highlights. Hmm. Why is that?

 Anyway, there's a lot of scripts to do that but I  couldn't  find  one
 that  simply  issues  a  terminal  bell  and nothing more. They're all
 pretty complex. Dunno why.

 The following script does the job:

   1   import weechat as w

   2   w.register("bell-highlight", "Vain", "1.0", "GPL3", "Beep", "", "")
   3   w.hook_signal("weechat_highlight", "handle_highlight", "")

   4   def handle_highlight(data, signal, signal_data):
   5       with open("/dev/tty", "w+") as tty:
   6           tty.write("\a")
   7       return w.WEECHAT_RC_OK

 It's so simple that I keep thinking: "There must be a builtin  way  to
 do this."