Review Request #12261 — Created April 26, 2022 and submitted
TestCase.create_rbclient(), which sets up and returns
RBClientinstance with a
URLMapTransport. It also introduces
get_rbclient_transport(), which returns the private transport
attribute from the client (to keep test code from having to access that
internal, which we may later decide to change).
Used this in some in-progress unit tests. All tests passed.