With the API changes in RBTools 6, a few of the things we were doing for mocking with unit tests were failing. There were two types of errors being hit: 1. We now handle `NotImplementedError` for cases where an API payload does not contain a link, instead of just assuming that the method won't exist on the class. This is necessary because we now have API stubs present on the resource classes. 2. Always pass in a payload and token for ListResource instantiation. Testing Done: Ran unit tests.