Update appveyor.yml
Update appveyor.yml

install six (needed for tests)
vmuriart/pythonnet,yagweb/pythonnet,vmuriart/pythonnet,pythonnet/pythonnet,AlexCatarino/pythonnet,QuantConnect/pythonnet,dmitriyse/pythonnet,yagweb/pythonnet,yagweb/pythonnet,yagweb/pythonnet,QuantConnect/pythonnet,vmuriart/pythonnet,AlexCatarino/pythonnet,denfromufa/pythonnet,AlexCatarino/pythonnet,denfromufa/pythonnet,Konstantin-Posudevskiy/pythonnet,AlexCatarino/pythonnet,dmitriyse/pythonnet,denfromufa/pythonnet,Konstantin-Posudevskiy/pythonnet,pythonnet/pythonnet,QuantConnect/pythonnet,Konstantin-Posudevskiy/pythonnet,pythonnet/pythonnet,dmitriyse/pythonnet