Failures with `create-backup` doesn't surface the error

[hloeung]

Steps to reproduce

1. juju run postgresql/5 create-backup --wait 60m
2. juju show-operation 109

Expected behavior

On errors, the full error should be shown, or at least a reason as to why it failed rather than an incomplete error message.

Actual behavior

Versions

Operating system: ubuntu@22.04
Juju CLI: 3.6.3-ubuntu-amd64
Juju agent: 3.6.1
Charm revision: 14/stable 553

Log output

Juju debug log:

Additional context

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The internal ticket has been created: https://warthogs.atlassian.net/browse/DPE-6837.

This message was autogenerated

[hloeung]

In this case, it looks to be ERROR: [082]: WAL segment 0000000A0000000000000060 was not archived before the 60000ms timeout

Maybe it should show the ERROR lines from the backup.log file?