destroy_libvirt_network causes hook error in nova-lxd use cases

[Ryan Beisner]

The recent addition of destroy_libvirt_network to the nova-compute charm @ master caused nova-lxd test cases to start failing, as virsh isn't present.

2016-07-15 00:57:22 INFO config-changed Traceback (most recent call last):
2016-07-15 00:57:22 INFO config-changed File "/var/lib/juju/agents/unit-nova-compute-0/charm/hooks/config-changed", line 500, in <module>
2016-07-15 00:57:22 INFO config-changed main()
2016-07-15 00:57:22 INFO config-changed File "/var/lib/juju/agents/unit-nova-compute-0/charm/hooks/config-changed", line 493, in main
2016-07-15 00:57:22 INFO config-changed hooks.execute(sys.argv)
2016-07-15 00:57:22 INFO config-changed File "/var/lib/juju/agents/unit-nova-compute-0/charm/hooks/charmhelpers/core/hookenv.py", line 715, in execute
2016-07-15 00:57:22 INFO config-changed self._hooks[hook_name]()
2016-07-15 00:57:22 INFO config-changed File "/var/lib/juju/agents/unit-nova-compute-0/charm/hooks/charmhelpers/contrib/openstack/utils.py", line 1802, in wrapped_f
2016-07-15 00:57:22 INFO config-changed restart_functions)
2016-07-15 00:57:22 INFO config-changed File "/var/lib/juju/agents/unit-nova-compute-0/charm/hooks/charmhelpers/core/host.py", line 526, in restart_on_change_helper
2016-07-15 00:57:22 INFO config-changed r = lambda_f()
2016-07-15 00:57:22 INFO config-changed File "/var/lib/juju/agents/unit-nova-compute-0/charm/hooks/charmhelpers/contrib/openstack/utils.py", line 1801, in <lambda>
2016-07-15 00:57:22 INFO config-changed (lambda: f(*args, **kwargs)), restart_map, stopstart,
2016-07-15 00:57:22 INFO config-changed File "/var/lib/juju/agents/unit-nova-compute-0/charm/hooks/charmhelpers/contrib/hardening/harden.py", line 79, in _harden_inner2
2016-07-15 00:57:22 INFO config-changed return f(*args, **kwargs)
2016-07-15 00:57:22 INFO config-changed File "/var/lib/juju/agents/unit-nova-compute-0/charm/hooks/config-changed", line 155, in config_changed
2016-07-15 00:57:22 INFO config-changed destroy_libvirt_network('default')
2016-07-15 00:57:22 INFO config-changed File "/var/lib/juju/agents/unit-nova-compute-0/charm/hooks/nova_compute_utils.py", line 608, in destroy_libvirt_network
2016-07-15 00:57:22 INFO config-changed out = check_output(['virsh', 'net-list']).split('\n')
2016-07-15 00:57:22 INFO config-changed File "/usr/lib/python2.7/subprocess.py", line 567, in check_output
2016-07-15 00:57:22 INFO config-changed process = Popen(stdout=PIPE, *popenargs, **kwargs)
2016-07-15 00:57:22 INFO config-changed File "/usr/lib/python2.7/subprocess.py", line 711, in __init__
2016-07-15 00:57:22 INFO config-changed errread, errwrite)
2016-07-15 00:57:22 INFO config-changed File "/usr/lib/python2.7/subprocess.py", line 1343, in _execute_child
2016-07-15 00:57:22 INFO config-changed raise child_exception
2016-07-15 00:57:22 INFO config-changed OSError: [Errno 2] No such file or directory
2016-07-15 00:57:22 INFO juju.worker.uniter.context context.go:579 handling reboot
2016-07-15 00:57:22 ERROR juju.worker.uniter.operation runhook.go:107 hook "config-changed" failed: exit status 1
2016-07-15 00:57:22 DEBUG juju.worker.uniter modes.go:31 [AGENT-STATUS] failed: run config-changed hook

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/342963
Committed: https://git.openstack.org/cgit/openstack/charm-nova-compute/commit/?id=39d0628dfb49d7b7b008c90bb07c9ef5b390767d
Submitter: Jenkins
Branch: master

commit 39d0628dfb49d7b7b008c90bb07c9ef5b390767d
Author: David Ames <email address hidden>
Date: Fri Jul 15 10:01:48 2016 -0700

    Add exception handling for unavailable virsh

    When virt-type is lxd libvirt-bin is not installed. The call to
    destroy_libvirt_network fails because virsh is not available.

    Add exception handling to destroy_libvirt_network when virt-type is lxd and
    virsh is unavailable.

    Closes-Bug: 1603566
    Change-Id: I448598d5160c183de46938999db1c9d5232b80b2