I know this is an old question, but I've been struggling with this issue all day, as part of the 'collectstatic' operation. I suddenly realised that this (manage.py collectstatic) is run in build (in my case in GitHub Actions), and not on Azure, and so of course doesn't have access to the Azure environment variables.

Collectstatic also doesn't need them, so I've updated my settings module to ignore anything that's not set in the environment, and it gets through the build process fine now.