juju models reports an error on half-dead model

Note that this failure was also seen as intermittent failures in CI like:
http://qa.jujucharms.com/releases/6057/job/model-migration-azure-arm/attempt/1071

The code in question is doing:
 if !remaining.IsEmpty() {
  // XXX: What error is appropriate? Do we need to care about models that its ok to be missing?
  return errors.Errorf("could not find settings/config for models: %v", remaining.SortedValues())
 }

we just need to figure out what the *right* behavior is.
Do we report a model, just without extra information.
Do we omit the model entirely? (I think this is probably the correct behavior).

The really easy fix that I'm playing with is:
diff --git a/state/modelsummaries.go b/state/modelsummaries.go
index 923be6b..29b50db 100644
--- a/state/modelsummaries.go
+++ b/state/modelsummaries.go
@@ -162,7 +162,7 @@ func (p *modelSummaryProcessor) fillInFromConfig() error {
        }
        if !remaining.IsEmpty() {
                // XXX: What error is appropriate? Do we need to care about models that its ok to be missing?
- return errors.Errorf("could not find settings/config for models: %v", remaining.SortedValues())
+ // return errors.Errorf("could not find settings/config for models: %v", remaining.SortedValues())
        }
        return nil
 }

Essentially, just don't worry if the model's config doc goes missing.

While watching "juju models --format=yaml" I can see it going into this state:
...
- name: admin/ma30
  short-name: ma30
  model-uuid: 02533045-2e87-4047-8c20-973747bf0375
  controller-uuid: 2c6b2b72-7c30-46dc-8368-a7680fad3aa3
  controller-name: lxd
  owner: admin
  cloud: lxd
  type: lxd
  life: dead
  status:
    current: destroying
    message: tearing down cloud environment
    since: just now
  access: admin
  last-connection: 2 seconds ago
  sla-owner: admin
  agent-version: 2.3.2.2
- name: admin/mb30
  short-name: mb30
  model-uuid: 9f6c0753-322b-4143-8cb6-5034a9bcd895
  controller-uuid: 2c6b2b72-7c30-46dc-8368-a7680fad3aa3
  controller-name: lxd
  owner: admin
  cloud: lxd
  type: lxd
  life: dead
  status:
    current: available
    since: just now
  access: admin
  last-connection: 3 seconds ago
  sla-owner: admin

I've also seen status: {}

But this means that the Model itself is going to Dead, even though we are still doing things. In that second model, we even see status as "available" even though the life is dead.
The latter is being read from the Statuses collection, while the former is from the Models and Settings collections.

So there is an argument that Model.Life attribute should be "dying" in these circumstances, and not "dead", but for now, we can just return them naturally.

https://github.com/juju/juju/pull/8201

I am sure that the above PR has been merged into develop (2.4+) as part of a bigger merge.