[BUGFIX] IRC bridge: Use connection initialized from aio_reactor.

Additionally, pin the irc library version to 18.0 because the newer
version has an error in the AioReactor:
```
  File "/home/rht/code/venv/lib/python3.8/site-packages/irc/bot.py", line 108, in run
    self.bot.reactor.scheduler.execute_after(intvl, self.check)
AttributeError: 'AioReactor' object has no attribute 'scheduler'
```

Author: rht

zulip/integrations/bridge_with_irc/irc_mirror_backend.py

@@ -30,7 +30,7 @@ def connect(self, *args: Any, **kwargs: Any) -> None:
         # Taken from
         # https://github.com/jaraco/irc/blob/master/irc/client_aio.py,
         # in particular the method of AioSimpleIRCClient
-        self.reactor.loop.run_until_complete(
+        self.c = self.reactor.loop.run_until_complete(
             self.connection.connect(*args, **kwargs)
         )
         print("Listening now. Please send an IRC message to verify operation")
@@ -65,16 +65,16 @@ def forward_to_irc(msg: Dict[str, Any]) -> None:
                 at_the_specified_subject = msg["subject"].casefold() == self.topic.casefold()
                 if in_the_specified_stream and at_the_specified_subject:
                     msg["content"] = ("@**%s**: " % msg["sender_full_name"]) + msg["content"]
-                    send = lambda x: c.privmsg(self.channel, x)
+                    send = lambda x: self.c.privmsg(self.channel, x)
                 else:
                     return
             else:
                 recipients = [u["short_name"] for u in msg["display_recipient"] if
                               u["email"] != msg["sender_email"]]
                 if len(recipients) == 1:
-                    send = lambda x: c.privmsg(recipients[0], x)
+                    send = lambda x: self.c.privmsg(recipients[0], x)
                 else:
-                    send = lambda x: c.privmsg_many(recipients, x)
+                    send = lambda x: self.c.privmsg_many(recipients, x)
             for line in msg["content"].split("\n"):
                 send(line)
 

zulip/integrations/bridge_with_irc/requirements.txt

@@ -1 +1 @@
-irc>=16.4
+irc==18.0