[2.2b3] mDNS observer traceback

Just saw this in rackd.log:

Traceback (most recent call last):
Failure: twisted.internet.error.ProcessTerminated: A process has ended with a probable error condition: process ended with exit code 1.
2017-03-18 02:01:21 provisioningserver.utils.services: [info] mDNS observation process started.
2017-03-18 02:01:22 -: [critical] Unhandled Error
 Traceback (most recent call last):
   File "/usr/lib/python3/dist-packages/twisted/python/log.py", line 101, in callWithLogger
     return callWithContext({"system": lp}, func, *args, **kw)
   File "/usr/lib/python3/dist-packages/twisted/python/log.py", line 84, in callWithContext
     return context.call({ILogContext: newCtx}, func, *args, **kw)
   File "/usr/lib/python3/dist-packages/twisted/python/context.py", line 118, in callWithContext
     return self.currentContext().callWithContext(ctx, func, *args, **kw)
   File "/usr/lib/python3/dist-packages/twisted/python/context.py", line 81, in callWithContext
     return func(*args,**kw)
 --- <exception caught here> ---
   File "/usr/lib/python3/dist-packages/twisted/internet/posixbase.py", line 597, in _doReadOrWrite
     why = selectable.doRead()
   File "/usr/lib/python3/dist-packages/twisted/internet/process.py", line 280, in doRead
     return fdesc.readFromFD(self.fd, self.dataReceived)
   File "/usr/lib/python3/dist-packages/twisted/internet/fdesc.py", line 94, in readFromFD
     callback(output)
   File "/usr/lib/python3/dist-packages/twisted/internet/process.py", line 283, in dataReceived
     self.proc.childDataReceived(self.name, data)
   File "/usr/lib/python3/dist-packages/twisted/internet/process.py", line 937, in childDataReceived
     self.proto.childDataReceived(name, data)
   File "/usr/lib/python3/dist-packages/twisted/internet/protocol.py", line 604, in childDataReceived
     self.outReceived(data)
   File "/usr/lib/python3/dist-packages/provisioningserver/utils/services.py", line 79, in outReceived
     self.outLineReceived(line)
   File "/usr/lib/python3/dist-packages/provisioningserver/utils/services.py", line 107, in outLineReceived
     self.objectReceived(obj)
   File "/usr/lib/python3/dist-packages/provisioningserver/utils/services.py", line 110, in objectReceived
     self._callback([obj])
   File "/usr/lib/python3/dist-packages/provisioningserver/rackdservices/networks_monitoring_service.py", line 73, in reportMDNSEntries
     d.addCleanup(lambda client: client(
 builtins.AttributeError: 'Deferred' object has no attribute 'addCleanup'

2017-03-18 02:01:24 provisioningserver.utils.services: [info] observe-mdns: Traceback (most recent call last):
2017-03-18 02:01:24 provisioningserver.utils.services: [info] observe-mdns: File "/usr/sbin/maas-rack", line 85, in <module>
2017-03-18 02:01:24 provisioningserver.utils.services: [info] observe-mdns: main()
2017-03-18 02:01:24 provisioningserver.utils.services: [info] observe-mdns: File "/usr/sbin/maas-rack", line 81, in main
2017-03-18 02:01:24 provisioningserver.utils.services: [info] observe-mdns: run()
2017-03-18 02:01:24 provisioningserver.utils.services: [info] observe-mdns: File "/usr/sbin/maas-rack", line 52, in run
2017-03-18 02:01:24 provisioningserver.utils.services: [info] observe-mdns: from provisioningserver.__main__ import main
2017-03-18 02:01:24 provisioningserver.utils.services: [info] observe-mdns: File "/usr/lib/python3/dist-packages/provisioningserver/__main__.py", line 44, in <module>
2017-03-18 02:01:24 provisioningserver.utils.services: [info] observe-mdns: main()
2017-03-18 02:01:24 provisioningserver.utils.services: [info] observe-mdns: File "/usr/lib/python3/dist-packages/provisioningserver/utils/script.py", line 97, in __call__
2017-03-18 02:01:24 provisioningserver.utils.services: [info] observe-mdns: self.execute(argv)
2017-03-18 02:01:24 provisioningserver.utils.services: [info] observe-mdns: File "/usr/lib/python3/dist-packages/provisioningserver/utils/script.py", line 92, in execute
2017-03-18 02:01:24 provisioningserver.utils.services: [info] observe-mdns: args.handler.run(args)
2017-03-18 02:01:24 provisioningserver.utils.services: [info] observe-mdns: File "/usr/lib/python3/dist-packages/provisioningserver/utils/avahi.py", line 213, in run
2017-03-18 02:01:24 provisioningserver.utils.services: [info] observe-mdns: _observe_mdns(reader, output, args.verbose)
2017-03-18 02:01:24 provisioningserver.utils.services: [info] observe-mdns: File "/usr/lib/python3/dist-packages/provisioningserver/utils/avahi.py", line 143, in _observe_mdns
2017-03-18 02:01:24 provisioningserver.utils.services: [info] observe-mdns: print(json.dumps(event), file=output, flush=True)
2017-03-18 02:01:24 provisioningserver.utils.services: [info] observe-mdns: BrokenPipeError: [Errno 32] Broken pipe
2017-03-18 02:01:24 provisioningserver.utils.services: [info] observe-mdns: Exception ignored in: <_io.TextIOWrapper name='<stdout>' encoding='UTF-8'>
2017-03-18 02:01:24 provisioningserver.utils.services: [info] observe-mdns: BrokenPipeError: [Errno 32] Broken pipe
2017-03-18 02:01:25 provisioningserver.utils.services: [critical] mDNS observation process failed.

Traceback (most recent call last):
Failure: twisted.internet.error.ProcessTerminated: A process has ended with a probable error condition: process ended with exit code 1.