Add a socket timeout for the mail worker

A mail worker is a long running application. And sometimes, the IMAP server
just hangs for hours for no apparent reason. imaplib doesn't enable setting
a timeout, and setting it globally seems fine.

todo/management/commands/mail_worker.py

@@ -1,16 +1,21 @@
 import logging
+import socket
 import sys
 
-from django.core.management.base import BaseCommand, CommandError
+from django.core.management.base import BaseCommand
 from django.conf import settings
 
 logger = logging.getLogger(__name__)
 
 
+DEFAULT_IMAP_TIMEOUT = 20
+
+
 class Command(BaseCommand):
     help = "Starts a mail worker"
 
     def add_arguments(self, parser):
+        parser.add_argument("--imap_timeout", type=int, default=30)
         parser.add_argument("worker_name")
 
     def handle(self, *args, **options):
@@ -22,10 +27,17 @@ class Command(BaseCommand):
         tracker = settings.TODO_MAIL_TRACKERS.get(worker_name, None)
         if tracker is None:
             logger.error(
-                f"couldn't find configuration for {worker_name} in TODO_MAIL_TRACKERS"
+                "couldn't find configuration for %r in TODO_MAIL_TRACKERS",
+                worker_name
             )
             sys.exit(1)
 
+        # set the default socket timeout (imaplib doesn't enable configuring it)
+        timeout = options["imap_timeout"]
+        if timeout:
+            socket.setdefaulttimeout(timeout)
+
+        # run the mail polling loop
         producer = tracker["producer"]
         consumer = tracker["consumer"]