glanceclient raises unhandled CommunicationError during glance service restart resulting in removed simplestreams-sync cron

[Chad Smith]

glance-simplestreams-sync only handles glanceclient.exc.ClientException and leaves the fastpoll cron job intact. But, glanceclient also raises exc.CommunicationError on a broken glance pipe due to glance service restart.

    return self._http_request(url, method, **kwargs)
  File "/usr/lib/python2.7/dist-packages/glanceclient/common/http.py", line 235, in _http_request
    raise exc.CommunicationError(message=message)
CommunicationError: Error communicating with http://10.1.7.237:9292 [Errno 32] Broken pipe

Full traceback: https://pastebin.canonical.com/156159/

 This unhandled error results in removal of the cron job and simplestreams-sync is then dead in the water and doesn't retry so waiting for the sync service to resurrect images is pointless.

I was able to succeed with the image sync running the script manually after the cron was removed per the above traceback showing that this error type was intermittent.

[Andreas Hasenack (ahasenack)]

Added landscape tasks to update the charm store revision for glance-simplestreams-sync once the fix lands there.