text/plain encoding for write_files unsupported?

[Steve Brasier]

OpenStack RockyLinux 8 instance failed to boot properly. Console log showed:

```
[ 103.927922] cloud-init[852]: Cloud-init v. 22.1-5.el8 running 'init' at Wed, 16 Nov 2022 14:45:47 +0000. Up 103.64 seconds.
<snip>
[ 103.974747] cloud-init[852]: 2022-11-16 14:45:47,803 - schema.py[WARNING]: Invalid cloud-config provided:
[ 103.978215] cloud-init[852]: write_files.0.encoding: 'text/plain' is not one of ['gz', 'gzip', 'gz+base64', 'gzip+base64', 'gz+b64', 'gzip+b64', 'b64', 'base64']
[ 103.982366] cloud-init[852]: write_files.0.encoding: 'text/plain' is not one of ['gz', 'gzip', 'gz+base64', 'gzip+base64', 'gz+b64', 'gzip+b64', 'b64', 'base64']
```

But the [docs](https://cloudinit.readthedocs.io/en/22.1_a/topics/modules.html#write-files) for this version so that text/plain IS an accepted encoding.

This worked before the release of RockyLinux 8.7 so I'm assuming this is a newer version of cloud-init and there's a regression?

[Steve Brasier (stevebrasier)]

Hmm. Logs from a non-upgraded RockyLinux 8.6 instance also show

```
Cloud-init v. 22.1-5.el8
```

[Chad Smith (chad.smith)]

We recently added user-data cloud-config schema validation to cloud-init turned it on to "warn" for potentially offending schema values. What you see here is a warning, and cloud-init still tries to honor the intent of the schema despite this warning.

This bug indicates that there was a bug in the schema definition which didn't represent the reality of all encoding type values actually supported.

This was fixed in upstream commit https://github.com/canonical/cloud-init/commit/02db659c95994b3bff58a372727fff377149c53b and I believe released in version 22.1-146-g02db659c9 (or offical 22.2 release).

to test tip of latest cloud-init to see if it still reproduces you can install cloud-init from our copr repo https://copr.fedorainfracloud.org/coprs/g/cloud-init/cloud-init-dev/, run cloud-init clean --logs --reboot to force a clean install on an affected system to see if it still generates the same warning.

[Chad Smith (chad.smith)]

Marking this as Fix released as I think it should already be in official 22.2 releases. If it still persists in 22.2 or later please feel free to reopen the bug.

[James Falcon (falcojr)]

Tracked in Github Issues as https://github.com/canonical/cloud-init/issues/4042