Code like this is dangerous:
class SimpleQueue(object):
queues = set()
because all instances will share the same 'queues' set object.
We don't really need multiple instances, but neither is there a reason to break
them. So do the normal Python thing instead.
(imported from commit a56bb8414dd549cfd312c9565df198cf9d20f08a)
Before this is deployed, we need to install rabbitmq and pika on the
target server (see the puppet part of this commit for how).
When this is deployed, we need to start the new user activity bot:
./manage.py process_user_activity
in the screen session on the relevant server, or user_activity logs
won't be processed (which will eventually result in all users getting
notifications about how their mirrors are out of date).
(imported from commit 44d605aca0290bef2c94fb99267e15e26b21673b)
