thread conditional code

[Just van Rossum]

Robin Becker wrote:

> I guess that answers my question; I can use locks without incurring any
> unnecessary overhead by starting the jitterbug and at least I can
> control access to contentious python objects. Foreign threads can do
> what they want anyhow.

Now what about when you'd want to be compatible with systems that don't
support the thread module?

Just