Add function to unregister a previously registered hook.

[rtibbles]

Summary

• Adds a function to unregister a previously registered hook

References

This was vendored into KDP in https://github.com/learningequality/kolibri-data-portal/pull/682

Reviewer guidance

Use it to unregister an otherwise previously registered hook.
Check that it is no longer a registered hook on its parent hook.

---

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

• PR has the correct target branch and milestone
• PR has 'needs review' or 'work-in-progress' label
• If PR is ready for review, a reviewer has been added. (Don't use 'Assignees')
• 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

[github-actions]

Build Artifacts

Asset type	Download link
PEX file	kolibri-0.16.1a0.dev0_git.17.g485dc924.pex
Windows Installer (EXE)	kolibri-0.16.1a0.dev0+git.17.g485dc924-windows-setup-unsigned.exe
Debian Package	kolibri_0.16.1a0.dev0+git.17.g485dc924-0ubuntu1_all.deb
Mac Installer (DMG)	kolibri-0.16.1a0.dev0+git.17.g485dc924-0.4.0.dmg
Android Package (APK)	kolibri-0.16.1a0.dev0+git.17.g485dc924-0.1.1-debug.apk
TAR file	kolibri-0.16.1a0.dev0+git.17.g485dc924.tar.gz
WHL file	kolibri-0.16.1a0.dev0+git.17.g485dc924-py2.py3-none-any.whl

[bjester]

Looks good to me, but before official approval, a question:

Are there any tests for the existing code? Just thinking it would be good to maintain same level of coverage on this module if there are

[bjester]

Not a blocker: some of this logic seems like it's getting a bit repetitive. There are subtle differences, but bulk of it seems like it could be consolidated. Every time I look at this area of the codebase, it takes me a while to carefully understand all of the conditions. Some consolidation can tuck that a way into a well commented chunk of code, so each usage can focus on its goal and what's different

[bjester]

Same comment here regarding consolidation. Seems this validation logic is pretty much the same as register_hook

[jredrejo]

Looks good for me, code is the same applied in https://github.com/learningequality/kolibri-data-portal/pull/682/ and it's already demostrating its utility in KDP in production.

As @bjester mentioned, tests would be a good to have, as usual, but I'm not going to be the one complaining for lack of testing. I'll love the day AI can create real and useful tests for us.

[rtibbles]

As I (re)-discovered when looking at this, there are no existing tests for this part of the code base - at least part of that is on me, as I didn't write any when I refactored this about 4 or 5 years ago. I am also happy to hold off merging to add some, I'll think on it.

[bjester]

If there is no existing test coverage, then no worries, we can merge and add tests later.