Run python tests during make check (#5226)

Run python tests during make check (#5226)

If building with python bindings, check the pytest is installed, and adds a command to run pytest after the existing make check tests. If built without python bindings, it just uses a null command. Note: the current semantics are such that the pytest tests will not run if the ctest run fails (unless you pass the correct flag to make to continue --ignore-errors I believe). I can look into changing this semantics if that would be preferred.