I've just updated to Tk 8.5 on OS X (Leopard, 10.5.1) and have rebuilt 
Python to link to the new version of Tk. I'm seeing tons of weird error 
messages in my logs when I run IDLE:

12/20/07 8:18:46 PM [0x0-0xa50a5].org.python.IDLE[1300] Break on 
__THE_PROCESS_HAS_FORKED_AND_YOU_CANNOT_USE_THIS_COREFOUNDATION_FUNCTION
ALITY___YOU_MUST_EXEC__() to debug. 
12/20/07 8:18:46 PM [0x0-0xa50a5].org.python.IDLE[1300] The process has 
forked and you cannot use this CoreFoundation functionality safely. You 
MUST exec(). 

I'm not sure if this is a showstopper bug or not, but I'm a bit 
concerned about all these error messages. Can someone investigate?

I would expect that this is a Tk bug, primarily, not a Python bug. If
somebody could reproduce it with Tk alone, it would be good to report it
at http://sourceforge.net/tracker/?group_id=12997

I already queried the Tcl-Mac mailing list about this to see if it 
should be reported as a bug against Tk. Daniel Steffen, the maintainer 
of Tcl/Tk on the Mac, thinks it may stem from Python-Tk interaction. His 
detailed reply is here:

http://www.nabble.com/Re%3A-Fork-vs.-exec-in-RC-5-of-Tk-8.5-
p14394315.html

I have not seen this error when running Tcl/Tk applications against 8.5-
-just Python-Tkinter.

Martin: Any response to Kevin's URL reference?

Let's close this issue as very old and obsolete.

Yes, whatever the initial problem, it doesn't seem to be an issue anymore.