[Tutor] Generate Prime Numbers

[Laura Creighton]

Alas, PyPy STM only works for 64 bit linux for now.  You are catching
the PyPy project at the edge of its 'bleeding edge research'.  We think
in 1 or 2 releases windows users should be able to get it too, and
I will let you know when that happens. And no promises.  These sorts of
things have a habit of being 'a simple matter of this and that' on paper
but actually much harder when it comes to writing code, so while it
will happen, when is an open question.

Sorry about that,
Laura