Comment 2 for bug 1866106

The problem is in oslo.config I think right here:

https://github.com/openstack/oslo.config/blob/20a7cee3e3019d60c4b367bb76922a1db41d1750/oslo_config/types.py#L142

That's coercing the value None to a string 'None' so it fails. According to Ben Nemec:

(02:13:48 PM) bnemec: The only way for a config opt to have a None value is for that to be the default and for the opt to be unset.
(02:14:14 PM) bnemec: So completely absent from the file, not something like "opt="

But that seems like a bug because I would think that code could be smarter about not coercing the value if the value is None, None is a valid choice and a default is set (so you need to override the default).