Comment 3 for bug 1648719

Another approach could be to change charm-keystone to use identity API v3 for managing Keystone regardless of preferred-api-version setting. Add function that detects API support on Keystone server and use that as basis for which manager class we use.

preferred-api-version=2 setting should of course still export api_version=2 relation data and set up the catalog and endpoints as the user would expect.