SE-3149 Fix the theme compilation issue in juniper

[pkulkark]

CachedStaticFilesStorage is deprecated in Django 2.2. It's plugin model i.e. CachedFilesMixin was being used in theme asset compilation. This was leading to inconsistent theme asset compilation and would lead to failures if more than one instance is used for load-balancing. This PR replaces the deprecated CachedFilesMixin with ManifestFilesMixin. It also fixes the order of the modules used in compilation.

Jira Tickets: OSPR-4966

Dependecies: None

Sandbox URL: TBD - sandbox is being provisioned

Merge deadline: None

Testing Instructions:

1. Spawn a new edX juniper instance and check the css files generated in /edx/var/edxapp/staticfiles/css.
2. Run paver update_assets command and recheck that no new css files are generated in /edx/var/edxapp/staticfiles/css.
3. Spawn multiple instances and add to load-balancer. Verify that the assets are getting loaded correctly.

Reviewers:

• @Kelketek
• edX reviewer[s] TBD

[openedx-webhooks]

Thanks for the pull request, @pkulkark! I've created OSPR-4966 to keep track of it in JIRA, where we prioritize reviews. Please note that it may take us up to several weeks or months to complete a review and merge your PR.

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Please let us know once your PR is ready for our review and all tests are green.

[Kelketek]

jenkins run all

[Kelketek]

👍

• I tested this: Verified these changes produce consistent asset file compilation.
• I read through the code

[natabene]

@pkulkark Thank you for your contribution. Please let me know once this is ready for our review.

[pkulkark]

@natabene I can't seem to get the jenkins tests running. Could you trigger it for me? Thanks!

[natabene]

jenkins run all

[nedbat]

Does this correspond to a change on master? Does master need the same fix?

[pkulkark]

@nedbat Yes it looks like master will need the same fix. This would need to be present since the juniper release so should I create another PR against master?
@natabene I see the message "There are no nodes with the label ‘juniper-worker’" in the console of the jenkins jobs. Is there something I need to do about it?

[nedbat]

@pkulkark Generally we prefer fixes to go on master first, and then be cherry-picked onto the release branch. This helps confirm the fix.
We're still working on getting the Juniper test workers going, there's nothing you need to do.

[pkulkark]

@nedbat I see. I opened #24990 against master. Closing this one in favor of #24990.

[openedx-webhooks]

@pkulkark Even though your pull request wasn’t merged, please take a moment to answer a two question survey so we can improve your experience in the future.

[edx-status-bot]

Your PR has finished running tests. The following contexts failed:

• jenkins/python-3.8/a11y
• jenkins/python-3.8/js
• jenkins/juniper/a11y
• jenkins/juniper/js
• jenkins/juniper/quality
• jenkins/juniper/python
• jenkins/python-3.8/python
• jenkins/python
• jenkins/quality
• jenkins/python-3.8/quality