Openstack nova compute services fails after yum update on compute nodes

Issue

• Openstack -nova compute service not starting after yum update

2016-07-19 13:39:28.879 7481 ERROR nova.virt.driver [-] Unable to load the virtualization driver
2016-07-19 13:39:28.879 7481 TRACE nova.virt.driver Traceback (most recent call last):
2016-07-19 13:39:28.879 7481 TRACE nova.virt.driver   File "/usr/lib/python2.7/site-packages/nova/virt/driver.py", line 1323, in load_compute_driver
2016-07-19 13:39:28.879 7481 TRACE nova.virt.driver     virtapi)
2016-07-19 13:39:28.879 7481 TRACE nova.virt.driver   File "/usr/lib/python2.7/site-packages/nova/openstack/common/importutils.py", line 52, in import_object_ns
2016-07-19 13:39:28.879 7481 TRACE nova.virt.driver     return import_class(import_str)(*args, **kwargs)
2016-07-19 13:39:28.879 7481 TRACE nova.virt.driver   File "/usr/lib/python2.7/site-packages/nova/openstack/common/importutils.py", line 33, in import_class
2016-07-19 13:39:28.879 7481 TRACE nova.virt.driver     traceback.format_exception(*sys.exc_info())))
2016-07-19 13:39:28.879 7481 TRACE nova.virt.driver ImportError: Class LibvirtDriver cannot be found (['Traceback (most recent call last):\n', '  File "/usr/lib/python2.7/site-packages/nova/openstack/common/importutils.py", line 29, in import_class\n    return getattr(sys.modules[mod_str], class_str)\n', "AttributeError: 'module' object has no attribute 'LibvirtDriver'\n"])
2016-07-19 13:39:28.879 7481 TRACE nova.virt.driver
2016-07-19 13:39:29.569 7614 INFO nova.openstack.common.periodic_task [-] Skipping periodic task _periodic_update_dns because its interval is negative
2016-07-19 13:39:29.605 7614 ERROR stevedore.extension [-] Could not load 'file': cannot import name util
2016-07-19 13:39:29.605 7614 ERROR stevedore.extension [-] cannot import name util
2016-07-19 13:39:29.605 7614 TRACE stevedore.extension Traceback (most recent call last):
2016-07-19 13:39:29.605 7614 TRACE stevedore.extension   File "/usr/lib/python2.7/site-packages/stevedore/extension.py", line 162, in _load_plugins
2016-07-19 13:39:29.605 7614 TRACE stevedore.extension     verify_requirements,
2016-07-19 13:39:29.605 7614 TRACE stevedore.extension   File "/usr/lib/python2.7/site-packages/stevedore/extension.py", line 177, in _load_one_plugin
2016-07-19 13:39:29.605 7614 TRACE stevedore.extension     plugin = ep.load(require=verify_requirements)
2016-07-19 13:39:29.605 7614 TRACE stevedore.extension   File "/usr/lib/python2.7/site-packages/pkg_resources.py", line 2260, in load
2016-07-19 13:39:29.605 7614 TRACE stevedore.extension     entry = __import__(self.module_name, globals(),globals(), ['__name__'])
2016-07-19 13:39:29.605 7614 TRACE stevedore.extension   File "/usr/lib/python2.7/site-packages/nova/image/download/file.py", line 23, in <module>
2016-07-19 13:39:29.605 7614 TRACE stevedore.extension     import nova.virt.libvirt.utils as lv_utils
2016-07-19 13:39:29.605 7614 TRACE stevedore.extension   File "/usr/lib/python2.7/site-packages/nova/virt/libvirt/__init__.py", line 15, in <module>
2016-07-19 13:39:29.605 7614 TRACE stevedore.extension     from nova.virt.libvirt import driver
2016-07-19 13:39:29.605 7614 TRACE stevedore.extension   File "/usr/lib/python2.7/site-packages/nova/virt/libvirt/driver.py", line 59, in <module>
2016-07-19 13:39:29.605 7614 TRACE stevedore.extension     from eventlet import util as eventlet_util
2016-07-19 13:39:29.605 7614 TRACE stevedore.extension ImportError: cannot import name util