setup: silence warning of unknown option python_requires on distutils
/usr/lib/python2.7/distutils/dist.py:267: UserWarning: Unknown distribution
option: 'python_requires'
setup: forcibly include cext/pure packages in py2exe (
issue5625)
Since these modules are implicitly imported by policy.importmod(), py2exe
can't track them statically. cffi modules are excluded for now because they
wouldn't be useful in frozen (i.e. CPython) environment.