Comment 3 for bug 1870087

Here's a new traceback that may be related to the same underlying issue. We should harden all the affected codepaths.

2020-04-02 09:49:49,780 ERROR [MainThread] Can't keep landscape-manager running. Exiting.
2020-04-02 09:49:49,781 INFO [MainThread] Stopping client...
Traceback (most recent call last):
  File "/usr/bin/landscape-manager", line 8, in <module>
    run(sys.argv)
  File "/usr/lib/python3/dist-packages/landscape/client/manager/service.py", line 62, in run
    run_landscape_service(ManagerConfiguration, ManagerService, args)
  File "/usr/lib/python3/dist-packages/landscape/client/service.py", line 115, in run_landscape_service
    startApplication(application, False)
  File "/usr/lib/python3/dist-packages/twisted/application/app.py", line 690, in startApplication
    service.IService(application).startService()
  File "/usr/lib/python3/dist-packages/twisted/application/service.py", line 288, in startService
    service.startService()
  File "/usr/lib/python3/dist-packages/landscape/client/manager/service.py", line 41, in startService
    self.publisher.start()
  File "/usr/lib/python3/dist-packages/landscape/client/amp.py", line 45, in start
    self._port = self._reactor.listen_unix(socket_path, factory)
  File "/usr/lib/python3/dist-packages/landscape/lib/reactor.py", line 228, in listen_unix
    return self._reactor.listenUNIX(socket, factory, wantPID=True)
  File "/usr/lib/python3/dist-packages/twisted/internet/posixbase.py", line 397, in listenUNIX
    p.startListening()
  File "/usr/lib/python3/dist-packages/twisted/internet/unix.py", line 373, in startListening
    raise error.CannotListenError(None, self.port,
twisted.internet.error.CannotListenError: Couldn't listen on any:b'/var/lib/landscape/client/sockets/manager.sock': Cannot acquire lock.
2020-04-02 09:49:49,894 INFO [MainThread] Monitor stopped with config /etc/landscape/client.conf
2020-04-02 09:49:49,896 INFO [MainThread] 0 of 0 expected load average snapshot events (0.00%) occurred in the last 2.03s.
2020-04-02 09:49:49,896 INFO [MainThread] 0 of 0 expected memory/swap snapshot events (0.00%) occurred in the last 2.03s.
2020-04-02 09:49:49,897 INFO [MainThread] 0 of 0 expected mount info snapshot events (0.00%) occurred in the last 2.03s.
2020-04-02 09:49:49,897 INFO [MainThread] 0 of 0 expected temperature snapshot events (0.00%) occurred in the last 2.03s.
2020-04-02 09:49:49,897 INFO [MainThread] 0 of 0 expected CPU usage snapshot events (0.00%) occurred in the last 2.02s.
2020-04-02 09:49:49,897 INFO [MainThread] 0 of 0 expected Swift device usage snapshot events (0.00%) occurred in the last 2.02s.
2020-04-02 09:49:49,897 INFO [MainThread] 0 of 0 expected Ceph usage snapshot events (0.00%) occurred in the last 2.02s.
2020-04-02 09:49:50,787 INFO [MainThread] Broker stopped with config /etc/landscape/client.conf