Move CACHES import into function scope to prevent side effects.

[rtibbles]

Summary

• The default cache module involves module level access to the Kolibri OPTIONS object
• This results in evaluation and initialization of the plugin registry
• This causes an issue for anything importing from main expecting to be able to enable plugins, as the enabled plugins will not be properly registered

References

Fixes a reported issue for the Mac app.
I am hopeful that this behaviour would raise a runtime error in develop due to some stricter checking, but it might still need some follow up to prevent this happening in future.

Reviewer guidance

Test the mac app that is built from the WHL file from this PR and ensure it starts.

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Testing checklist

• Contributor has fully tested the PR manually
• If there are any front-end changes, before/after screenshots are included
• Critical user journeys are covered by Gherkin stories
• Critical and brittle code paths are covered by unit tests

PR process

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• If this is an important user-facing change, PR or related issue has a 'changelog' label
• If this includes an internal dependency change, a link to the diff is provided

Reviewer checklist

• Automated test coverage is satisfactory
• PR is fully functional
• PR has been tested for accessibility regressions
• External dependency files were updated if necessary (yarn and pip)
• Documentation is updated
• Contributor is in AUTHORS.md

[jredrejo]

No doubt, thanks. I think I was who introduced the problem :(

[radinamatic]

@pcenov also confirmed that it installs and runs on the Mac device, we are good to go! 💯

[rtibbles]

I think I was who introduced the problem :(

Yes - but the fact that nothing shouts at you if an import like this is added is the real problem here!