Import fixes for Python 3
Import fixes for Python 3

Summary: As title

Differential Revision: D5135990

fbshipit-source-id: 88cb15bb2fb97dd21faf3ea5ddb8d4dbff7fad93

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