ERROR cannot deploy bundle, invalid fields

[Felipe Reyes]

There is a pull request that was recently merged[0], this change breaks the deployment of the bundles used by Zaza and FCE at the very least

$ juju deploy -m openidc ./tests/bundles/focal-yoga.yaml
ERROR cannot deploy bundle, invalid fields: unmarshal document 0: yaml: unmarshal errors:
  line 1: field variables not found in bundle
  line 4: field local_overlay_enabled not found in bundle
  line 8: field comment not found in bundle

Over the years it has become a common practice to keep a section at the top of the bundles with variables that are referenced later, for example see https://opendev.org/openstack/charm-keystone/src/branch/master/tests/bundles/focal-yoga.yaml#L1

[0] https://github.com/juju/juju/pull/14427

[Felipe Reyes (freyes)]

This is the relevant section of the bundle, and the full bundle can be found at https://paste.ubuntu.com/p/YRxftNBpVS/

The key "local_overlay_enabled" is used by zaza ( https://github.com/openstack-charmers/zaza/blob/b393baaaaf4f71690a6a762f041af9353b8ca6b7/zaza/charm_lifecycle/deploy.py#L45 )

```
variables:
  openstack-origin: &openstack-origin cloud:focal-yoga

local_overlay_enabled: False

series: focal

comment:
- 'machines section to decide order of deployment. database sooner = faster'
machines:
  '0':
    constraints: mem=3072M
  '1':
    constraints: mem=3072M
  '2':
    constraints: mem=3072M

applications:
...
```

[Heather Lanigan (hmlanigan)]

This is in conflict with https://bugs.launchpad.net/juju/+bug/1983386 in some ways. We'll have to find a compromise.

The change should apply to local bundles only.

--force can be used to ignore the validation.

[Heather Lanigan (hmlanigan)]

Discussion of a solution here: https://chat.charmhub.io/charmhub/pl/8j3ccjzxzbr8uk9ru9csqe8kgo

[Heather Lanigan (hmlanigan)]

https://github.com/juju/juju/pull/14474