Building python on OSX Mavericks (10.9)
of Python 3.4 crashes when this is set:

MACOSX_DEPLOYMENT_TARGET=10.7

This happens with OSX 10.9.2,
all current updates installed,
as of 2014-04-28.

Demo script:
You can use my attached script to validate this error.
The script builds PySide for 16 configurations.
Exactly on Python 3.4 / OSX 10.7 it crashes.

You can easily tweak the creating loop to just build the crashing case.

Cheers -- Chris