Comment 11 for bug 1852412

When Juju updates a credential there are some checks that are testing its validity (the same checks are used during model migration to ensure completeness):

1. Based on the list of machines in Juju, can Juju *see* corresponding instances in the cloud?
2. Based on the instances that Juju can get from the cloud for *this* model, does it have corresponding machines?

Both checks are strict. However, (2) is more useful to model migration (did we manage to migrate all the machines correctly) than to a credential update. So, as part of the fix for this scenario, I'll relax current credential validity check to only use (1). [FIX PART 1]

In addition, a credential update can be forced. In other words, when a user is 100% sure that the credential is valid and needs to be used, via Juju API, a credential update can be forced to ignore the validity errors. I will expose this functionality to Juju CLI as well so that you can 'juju update-credential <cloud_name> <credentials_name> --controller <controller_name> --force' [FIX PART 2].

However, since Juju 2.7.0 is imminent, I'll put these fixes into 2.7.1. If/when we plan another 2.6 release, we may revisit the necessity to backport it. Meanwhile, thank you for detailing the workaround :D