cli: fix pluginerror in handle_url if json is True

[bastimeyer]

Fixes #4589

console.exit(msg) requires a str parameter, otherwise it'll try to serialize the unknown input type as JSON if args.json is True, which can fail:

streamlink/src/streamlink_cli/console.py

Lines 89 to 95 in 2a5b71f

	def exit(self, msg: str) -> None:
	if self.json:
	self.msg_json(error=msg)
	else:
	self.msg(f"error: {msg}")
	sys.exit(1)

As already said in other threads, the ConsoleOutput usage and handling of console.exit() is pretty bad and needs to be rewritten.

---

[mkbloke]

This bombed before; it is working as expected now, thanks.

$ streamlink https://www.yupptv.com/channels/asianet-news/liveXXX
[cli][info] Found matching plugin yupptv for URL https://www.yupptv.com/channels/asianet-news/liveXXX
error: Unable to open URL: https://www.yupptv.com/channels/asianet-news/liveXXX (404 Client Error: Not Found for url: https://www.yupptv.com/channels/asianet-news/liveXXX)

$ streamlink -j https://www.yupptv.com/channels/asianet-news/liveXXX
{
  "error": "Unable to open URL: https://www.yupptv.com/channels/asianet-news/liveXXX (404 Client Error: Not Found for url: https://www.yupptv.com/channels/asianet-news/liveXXX)"
}