I admit that the patch isn't ideal.  But it is a simple approach to fix the issue using pure Python.  A better solution would be to use synchronization routines provided by the OS, such as the pthread condition functions on *NIX systems and the Win32 API synchronization functions on Windows.

I wrote this patch to use with a simulator that may run for months at a time and will definitely run for days at a time.  If the run happens to occur when DST ends and the clock automatically changes, as is the case for most systems, the simulation could stall for one hour and produce undesirable results.

Having a sleeps depend on the wall clock is a bad idea.  But since that is what we are working with, wouldn't it be better to have results skewed by a fraction of a minute or even a second rather than be off by an hour?