Hotfix for upstream dependency's incompatibility with Django 4.1

[AetherUnbound]

Due to miracle2k/django-assets#102 (and the fact that we don't really have a way of migrating down when deploying), this is a hotfix that should still allow the manage.py assets build command to run.

To test locally, run just build then just manage assets build.

I've changed the post-compile script so that if any step fails, the whole build fails.

I've also added some CI/CD steps to check that assets can still be built.

[milktea02]

I wonder if it'd be worth forking django-assets or finding an active fork since it hasn't had an update since 2020

[AetherUnbound]

I wonder if it'd be worth forking django-assets or finding an active fork since it hasn't had an update since 2020

I know 😞 I've submitted miracle2k/django-assets#103 but I don't have high hopes it'll be merged/deployed any time soon. Def wanted to get a fix out first though as our site is presently broken 🤪