Revert D5879947: [caffe2][PR] Enable python3 builds
Revert D5879947: [caffe2][PR] Enable python3 builds

Summary:
This reverts commit c452362b2ab54397723b5be3f1258c57213f6fc4

bypass-lint

Differential Revision: D5879947

fbshipit-source-id: 9dfe4e17ea84c252fa75c103c7a267e1ceddab98

davinwang/caffe2,davinwang/caffe2,Yangqing/caffe2,caffe2/caffe2,pietern/caffe2,Yangqing/caffe2,Yangqing/caffe2,davinwang/caffe2,pietern/caffe2,pietern/caffe2,xzturn/caffe2,pietern/caffe2,xzturn/caffe2,xzturn/caffe2,pietern/caffe2,Yangqing/caffe2,davinwang/caffe2,sf-wind/caffe2,xzturn/caffe2,sf-wind/caffe2,Yangqing/caffe2,xzturn/caffe2,sf-wind/caffe2,sf-wind/caffe2,davinwang/caffe2,sf-wind/caffe2