Comment 2 for bug 1837199

I just recreated this locally on master in a local venv:

osboxes@osboxes:~/git/nova$ source .tox/shared/bin/activate
(shared) osboxes@osboxes:~/git/nova$ nova-manage cell_v2
An error has occurred:
Traceback (most recent call last):
  File "/home/osboxes/git/nova/.tox/shared/lib/python3.6/site-packages/oslo_config/cfg.py", line 3179, in __getattr__
    return getattr(self._conf._namespace, name)
AttributeError: '_Namespace' object has no attribute 'action_fn'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/osboxes/git/nova/nova/cmd/manage.py", line 2206, in main
    fn, fn_args, fn_kwargs = cmd_common.get_action_fn()
  File "/home/osboxes/git/nova/nova/cmd/common.py", line 169, in get_action_fn
    fn = CONF.category.action_fn
  File "/home/osboxes/git/nova/.tox/shared/lib/python3.6/site-packages/oslo_config/cfg.py", line 3181, in __getattr__
    raise NoSuchOptError(name)
oslo_config.cfg.NoSuchOptError: no such option action_fn in group [DEFAULT]

(shared) osboxes@osboxes:~/git/nova$ pip show oslo.config
Name: oslo.config
Version: 6.11.0
Summary: Oslo Configuration API
Home-page: https://docs.openstack.org/oslo.config/latest/
Author: OpenStack
Author-email: <email address hidden>
License: UNKNOWN
Location: /home/osboxes/git/nova/.tox/shared/lib/python3.6/site-packages
Requires: oslo.i18n, PyYAML, requests, six, rfc3986, debtcollector, netaddr, stevedore
Required-by: python-keystoneclient, pycadf, oslo.versionedobjects, oslo.upgradecheck, oslo.service, oslo.privsep, oslo.policy, oslo.middleware, oslo.messaging, oslo.log, oslo.db, oslo.concurrency, oslo.cache, os-win, os-vif, keystonemiddleware, castellan, nova
(shared) osboxes@osboxes:~/git/nova$