I appreciate that this rebinding to a user is more elegant in concept.  However, I'm concerned about doing this:  in `get_module_for_descriptor_internal` there are a bunch of inner function (like `publish` and `inner_get_module`) with "user" already bound as a closure, that are providing functions for System.  I'm not sure it's possible to rebind those, and so it might just be clearer to instantiate a new Module.