Add ONNX py3 CI cases (#21715)
Summary:
So far, we only have py2 ci for onnx. I think py3 support is important. And we have the plan to add onnxruntime backend tests, which only supports py3.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/21715
Reviewed By: bddppq
Differential Revision: D15796885
Pulled By: houseroad
fbshipit-source-id: 8554dbb75d13c57b67ca054446a13a016983326c
