Non-existing secret error message shouldn't display set contents such as "{non-existing-secret}"

[juditnovak]

Steps to reproduce

Use mongodb-operator unittests -> test_delete_password()

Expected behavior

Instead of expected "Non-existing secret {'ca-secret'}" it should be ""Non-existing secret(s) 'ca-secret', 'any-other-secret'..."

Actual behavior

See above

Versions

Operating system: any

Juju CLI: any with secrets

Juju agent: any with secrets

Log output

Juju debug log: None

Additional context

[github-actions[bot]]

https://warthogs.atlassian.net/browse/DPE-3312

[juditnovak]

Fixed in https://github.com/canonical/data-platform-libs/pull/131