Message 310316 - Python tracker

@Ned, it may be a little tight to land this given the time left before beta 1.  However, this is meant as a tool for us to use in the test suite (particularly to test the subinterpreter C-API).  So I'm arguing that, if necessary, it would still be okay to land this after the feature freeze.  (I'm still hoping to get this in before the cutoff.)  What do you think?