IRC: Handle error by displaying the error message.

The proper solution would be to handle each errors differently. But for
now, logging the message is at least informative to the user.

zulip/integrations/bridge_with_irc/irc_mirror_backend.py

@@ -1,3 +1,4 @@
+import logging
 import multiprocessing as mp
 import sys
 from typing import Any, Dict, Optional
@@ -141,3 +142,6 @@ class IRCBot(irc.bot.SingleServerIRCBot):
             except ValueError:
                 return
             self.dcc_connect(address, port)
+
+    def on_error(self, c: ServerConnection, e: Event) -> None:
+        logging.error("error from server: %s", e.target)