Comment 4 for bug 1824299

it's not possible for the target class to be imported but not be mapped, since it is using the declarative metaclass that maps the class immediately. The order of relationships has nothing to do with it, and the stack trace here occurs within the configure_mappers() phase which assumes all classes have been imported, and therefore it should not be possible that they exist but are not mapped. I need to look at this much more closely.