I decided to use `module.location` here, because the XModule compatibility layer already maps this to `scope_ids` (in [x_module.py](https://github.com/edx/edx-platform/blob/master/common/lib/xmodule/xmodule/x_module.py#L179-L184)).  I thought it might be easier to phase out the compatibility layer if we're using the same code path here that we use elsewhere.

But if it makes more sense to use `scope_ids` directly here, I can make that change.