I'm attaching three new patches following on from Eric and Christian's
suggestions:

check_mno_cywin_py27_1.patch (for Python 2.7)
check_mno_cywin_py3_1.patch (for Python 3.2 and 3.3)
check_mno_cywin_py34_1.patch (for Python 3.4)

The py27 patch now uses os.popen to avoid importing subprocess as
suggested by Eric. The other two patches are changed to use
check_output as suggested by Christian (subprocess is already imported
in 3.x).

I've retested the patches using the same setup as before and the
results are unchanged for all gcc and Python versions tested.