mod_python+trac+Leopard and 'process has forked, you must exec' error log

Hello,

First, my configuration:
- Mac OS X Leopard 10.5
-  trac installed from MacPorts (with Python 2.6.4)
- mod_python 3.3.1 from sources
- Apache 2 built-in from Leopard

Everything is working pretty well except that I'm getting lots of this  
messages in the apache error log when browsing trac:

The process has forked and you cannot use this CoreFoundation  
functionality safely. You MUST exec().
Break on  
__THE_PROCESS_HAS_FORKED_AND_YOU_CANNOT_USE_THIS_COREFOUNDATION_FUNCTIONALITY___YOU_MUST_EXEC__ 
() to debug.

Apache does not crash however.


I have read that php could do that but it seems the php apache module  
is not loaded here.
Any idea?


Thanks,
Thomas