Comment 2 for bug 2062988

I mistrust having cloud-init in the snap due to mis-match problem with the host system, and this bug is another version of that problem.

An older version of cloud-init is in the snap - SRU pending LP: #2056100 - and a newer version outside the snap. The copy of cloud-init in the snap is what is used to run `cloud-init schema --system`. I have attached a script that allows one to run arbitrary programs as if they were in the subiquity-like snap, and doing so with `cloud-init schema --system` shows the following:

+ cloud-init schema --system
Found cloud-config data types: user-data, network-config

1. user-data at /var/lib/cloud/instances/nocloud/cloud-config.txt:
Empty 'cloud-config' found at /var/lib/cloud/instances/nocloud/cloud-config.txt. Nothing to validate.

2. network-config at /var/lib/cloud/instances/nocloud/network-config.json:
  Invalid network-config /var/lib/cloud/instances/nocloud/network-config.json
  Error: Cloud config schema errors: config.0.subnets.0: Additional properties are not allowed ('broadcast' was unexpected)

Error: Invalid schema: network-config

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The options to resolve this and fix desktop netboot appear to be:
1. rebuild snaps with cloud-init 24.1.3, either after SRU or forcing the issue now with PPA tricks
2. run `cloud-init schema --system` not from the snap, but from the host
3. adjust handling after `cloud-init schema --system` so that it is not allowed to fail the install