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> 
> 	auth_url is actually a dynamic parameter and depends on the
> keystone auth plugin used
> 	(auth_type=xxx). The plugin which needs this parameter, registers it.
> 
> 
> 
> Based on this http://paste.openstack.org/show/612664/ I would say that the
> plugin doesn't register it :( It either can be a bug, or it was done intentionally,
> I don't know.
> 
It should register it after you load it, via keystonauth1.loading.load_auth_plugin_from_conf_options()
There are also register_auth_conf_options() and get_auth_plugin_conf_options,  which I think are mainly used 
for listing the most used plugins' options in the debug log. But I don't think it would be wise
just to choose a plugin and register its options for auth_url, because it is ugly, I think, and can lead to
other problems.
 
> 
> My final thought that we have to use both (auth_url and auth_uri) options in
> mistral config, which looks ugly, but necessary.

It's not just Mistral, but every component which uses keystonemiddleware.

> 
> Best,
> Mike
Br,
György