Python 3 wheels for Windows x64 aren't getting built

[soltanmm]

And I don't know why the Py3 builds are reported as 'succeeding' anyway on the Windows builders.

Setting for 1.1 as a long-tail target because Python 3 support is still technically in beta, but this issue is receiving immediate attention.

[tseaver]

The 3.4 Windows wheels are also not installable on Python 3.5, leading to gcloud Appveyor errors.

[nathanielmanistaatgoogle]

@kpayson64 spent some time on this in the last week (thanks!).

[nathanielmanistaatgoogle]

@tseaver: I'm not sure I understand your comment - are you saying that there is a circumstance in which you are able to pip install --upgrade --pre grpcio on Windows with Python 3.4 but not (with the same Windows and underlying system) not Python 3.5?

[tseaver]

@nathanielmanistaatgoogle The Appveyor builds succeed for Python 3.4 32-bit, but fail for Python 3.4 64-bit and for both Python 3.5 32-bit and 64-bit: https://ci.appveyor.com/project/dhermes/gcloud-python