Message 254923 - Python tracker

I should have commented more on the run_once removal.  The depiction given in its docstring seemed inconsistent with the new way stop works and I found no callers, so it seemed like it was best left out to avoid confusion.  No worries though, I didn't get to know that test module very well before messing with it.  It just came up in my scan for stop() callers.

Looks good, I've applied to a 3.5.0 build and will include it in my testing from now on.

Thanks Guido.