Intermittent traceback when enabling DPDK

[Frode Nordahl]

Zaza:
2022-10-13 14:44:00.688839 | focal-medium | 2022-10-13 14:44:00 [INFO] ERROR: test_enable_dpdk (zaza.openstack.charm_tests.ovn.tests.DPDKTest)
2022-10-13 14:44:00.688907 | focal-medium | 2022-10-13 14:44:00 [INFO] Confirm that transitioning to/from DPDK works.
2022-10-13 14:44:00.689048 | focal-medium | 2022-10-13 14:44:00 [INFO] ----------------------------------------------------------------------
2022-10-13 14:44:00.689185 | focal-medium | 2022-10-13 14:44:00 [INFO] Traceback (most recent call last):
2022-10-13 14:44:00.689327 | focal-medium | 2022-10-13 14:44:00 [INFO] File "/home/ubuntu/src/review.opendev.org/x/charm-ovn-chassis/src/.tox/func-target/lib/python3.8/site-packages/zaza/openstack/charm_tests/ovn/tests.py", line 306, in test_enable_dpdk
2022-10-13 14:44:00.689462 | focal-medium | 2022-10-13 14:44:00 [INFO] with self.config_change(
2022-10-13 14:44:00.689479 | focal-medium | 2022-10-13 14:44:00 [INFO] File "/usr/lib/python3.8/contextlib.py", line 113, in __enter__
2022-10-13 14:44:00.689495 | focal-medium | 2022-10-13 14:44:00 [INFO] return next(self.gen)
2022-10-13 14:44:00.689615 | focal-medium | 2022-10-13 14:44:00 [INFO] File "/home/ubuntu/src/review.opendev.org/x/charm-ovn-chassis/src/.tox/func-target/lib/python3.8/site-packages/zaza/openstack/charm_tests/test_utils.py", line 329, in config_change
2022-10-13 14:44:00.689688 | focal-medium | 2022-10-13 14:44:00 [INFO] model.wait_for_application_states(
2022-10-13 14:44:00.689705 | focal-medium | 2022-10-13 14:44:00 [INFO] File "/home/ubuntu/src/review.opendev.org/x/charm-ovn-chassis/src/.tox/func-target/lib/python3.8/site-packages/zaza/__init__.py", line 224, in _wrapper
2022-10-13 14:44:00.689718 | focal-medium | 2022-10-13 14:44:00 [INFO] return future.result(timeout)
2022-10-13 14:44:00.689734 | focal-medium | 2022-10-13 14:44:00 [INFO] File "/usr/lib/python3.8/concurrent/futures/_base.py", line 444, in result
2022-10-13 14:44:00.689746 | focal-medium | 2022-10-13 14:44:00 [INFO] return self.__get_result()
2022-10-13 14:44:00.689761 | focal-medium | 2022-10-13 14:44:00 [INFO] File "/usr/lib/python3.8/concurrent/futures/_base.py", line 389, in __get_result
2022-10-13 14:44:00.689812 | focal-medium | 2022-10-13 14:44:00 [INFO] raise self._exception
2022-10-13 14:44:00.689871 | focal-medium | 2022-10-13 14:44:00 [INFO] File "/home/ubuntu/src/review.opendev.org/x/charm-ovn-chassis/src/.tox/func-target/lib/python3.8/site-packages/zaza/__init__.py", line 209, in _runner
2022-10-13 14:44:00.689906 | focal-medium | 2022-10-13 14:44:00 [INFO] return await f(*args, **kwargs)
2022-10-13 14:44:00.689965 | focal-medium | 2022-10-13 14:44:00 [INFO] File "/home/ubuntu/src/review.opendev.org/x/charm-ovn-chassis/src/.tox/func-target/lib/python3.8/site-packages/zaza/model.py", line 1656, in async_wait_for_application_states
2022-10-13 14:44:00.690016 | focal-medium | 2022-10-13 14:44:00 [INFO] ok = check_unit_workload_status(
2022-10-13 14:44:00.690035 | focal-medium | 2022-10-13 14:44:00 [INFO] File "/home/ubuntu/src/review.opendev.org/x/charm-ovn-chassis/src/.tox/func-target/lib/python3.8/site-packages/zaza/model.py", line 1380, in check_unit_workload_status
2022-10-13 14:44:00.690066 | focal-medium | 2022-10-13 14:44:00 [INFO] check_model_for_hard_errors(model)
2022-10-13 14:44:00.690114 | focal-medium | 2022-10-13 14:44:00 [INFO] File "/home/ubuntu/src/review.opendev.org/x/charm-ovn-chassis/src/.tox/func-target/lib/python3.8/site-packages/zaza/model.py", line 1358, in check_model_for_hard_errors
2022-10-13 14:44:00.690157 | focal-medium | 2022-10-13 14:44:00 [INFO] raise UnitError(errored_units)
2022-10-13 14:44:00.690202 | focal-medium | 2022-10-13 14:44:00 [INFO] zaza.model.UnitError: Units ovn-chassis/1 in error state

Charm:
2022-10-13 14:43:58 ERROR unit.ovn-chassis/1.juju-log server.go:316 Hook error:
Traceback (most recent call last):
  File "/var/lib/juju/agents/unit-ovn-chassis-1/.venv/lib/python3.10/site-packages/charms/reactive/__init__.py", line 74, in main
    bus.dispatch(restricted=restricted_mode)
  File "/var/lib/juju/agents/unit-ovn-chassis-1/.venv/lib/python3.10/site-packages/charms/reactive/bus.py", line 390, in dispatch
    _invoke(other_handlers)
  File "/var/lib/juju/agents/unit-ovn-chassis-1/.venv/lib/python3.10/site-packages/charms/reactive/bus.py", line 359, in _invoke
    handler.invoke()
  File "/var/lib/juju/agents/unit-ovn-chassis-1/.venv/lib/python3.10/site-packages/charms/reactive/bus.py", line 181, in invoke
    self._action(*args)
  File "/var/lib/juju/agents/unit-ovn-chassis-1/charm/reactive/ovn_chassis_charm_handlers.py", line 132, in configure_ovs
    charm_instance.configure_ovs(
  File "/var/lib/juju/agents/unit-ovn-chassis-1/charm/lib/charms/ovn_charm.py", line 180, in configure_ovs
    super().configure_ovs(sb_conn, mlockall_changed)
  File "/var/lib/juju/agents/unit-ovn-chassis-1/charm/lib/charms/ovn_charm.py", line 1151, in configure_ovs
    self.configure_ovs_hw_offload() | self.configure_ovs_dpdk())
  File "/var/lib/juju/agents/unit-ovn-chassis-1/charm/lib/charms/ovn_charm.py", line 1032, in configure_ovs_dpdk
    self.dpdk_eal_allow_devices(dpdk_context.devices())
  File "/var/lib/juju/agents/unit-ovn-chassis-1/charm/lib/charms/ovn_charm.py", line 998, in dpdk_eal_allow_devices
    if ch_core.host.cmp_pkgrevno('dpdk', '20.11.3') >= 0:
  File "/var/lib/juju/agents/unit-ovn-chassis-1/.venv/lib/python3.10/site-packages/charmhelpers/core/host_factory/ubuntu.py", line 110, in cmp_pkgrevno
    return apt_pkg.version_compare(current_ver.ver_str, revno)
AttributeError: 'NoneType' object has no attribute 'ver_str'