homepage

Yes I have a Mac and I am glad to help, so I gave it a test run tonight. The first thing I did was apply the patch then I ran idle from the console like so:
./python.exe Lib/idlelib/idle.py
For testing I used a simple print command to print to stderr:
sys.stderr.write("spam/n")
which I got the output of
spam/n6
I also tried to use the newer print function:
print("fatal error", file=sys.stderr)
Python 3.4 on the Mac behaved exactly the same way with or without the patch. I got the stderr output in the Python shell and nothing appeared in the console. With the patch applied I saw no dialog box to capture the stderr output. Maybe I didn't perform the test correctly?
Another thing to consider is for Mac IDLE runs in a special mode via macosxSupport.py which I turn on by forcing runningAsOSXApp() to always return True. Even after setting runningAsOSXApp() to true a dialog box does not appear when writing to stderr.
Maybe I am not testing this patch correctly? Let me know if I can do anything else to help, thanks.