🚀 Feature

register an error message to show to the user upon requesting an executor when an executor is not instantiated

Motivation & Pitch

NVFuser and other executors currently are only registered when their dependencies are available. That is good (error message > silent bad performance).
But how to get good error messages?

We (@KaelanDt ) looked at adding installation instructions into error messages at the recipe level, but it would be more awesome if we could have this with the (failing) executor instantiation and have an get_executor optionally raise the error message .