support: fix assert_python_ok() on python 3.3
support: fix assert_python_ok() on python 3.3

Python 3.3 doesn't support the -I command line option (isolated mode).

gvanrossum/asyncio,vxgmichel/asyncio,manipopopo/asyncio,jashandeep-sohi/asyncio,fallen/asyncio,jashandeep-sohi/asyncio,fallen/asyncio,gvanrossum/asyncio,vxgmichel/asyncio,haypo/trollius,haypo/trollius,1st1/asyncio,Martiusweb/asyncio,Martiusweb/asyncio,1st1/asyncio,gsb-eng/asyncio,ajdavis/asyncio,Martiusweb/asyncio,manipopopo/asyncio,ajdavis/asyncio,manipopopo/asyncio,ajdavis/asyncio,gvanrossum/asyncio,jashandeep-sohi/asyncio,haypo/trollius,1st1/asyncio,fallen/asyncio,vxgmichel/asyncio,gsb-eng/asyncio,gsb-eng/asyncio