I am thinking about just installing this manually on the worker ...

If you install them system wide (i.e. with sudo) and add agent.package_manager.system_site_packages then they will always be available for you 🙂

And then also use 

priority_optional_packages: ["carla"]

This actually means that it will always try to install the package clara first, but if it fails, it will no raise an error.

BTW: this would be a good use case for dockers, just saying 😉