Yeah -- seeing this, I can see the advantage of this, and I wouldn't want to reinvent the mock wheel.  (It it might prove to be useful elsewhere).

We should update the docs.  Since we now have automatic dependency resolution, we should update the `setupext.py` configuration for `Tests` as well.  And maybe, for good measure, in case all that fails, mark these tests as "skip" or "knownfail" if mock is not installed?