Add punt hook to drop admin-chosen messages

[dehnert]

Useful if there's a class with some useful messages, but also a high rate of messages that nobody needs to see that unnecessarily load the server.

[asedeno]

I'm not convinced I want this to be a function by default, but the idea is good. Do you want to filter on anything more than the class/instance/recipient tuple?

[dehnert]

My current function is:

def ROOST_CHECK_PUNT(notice):
    if (notice.cls == b'MOIRA' and notice.instance == b'incr-runner' and
        notice.sender == b'smstest@ATHENA.MIT.EDU' and
        len(notice.fields) >= 1 and
        b'pipe child exits with signal 0 status 0' in notice.fields[0]):
        return True
    return False

so I'm also matching on the body (on a theory that maybe I'm somewhat interested if there's a different error).

(Something else an arbitrary function allows is dropping some percentage of traffic, which might be appealing in some use-cases.)

[asedeno]

I understand why you want to do this, but now I've thought about it enough to realize why I don't like it: it can't be configured via config.yml at all, unlike everything else in this file. I'm going to think on this some more.