from tensorflow.core.protobuf import cluster_pb2 ImportError: cannot import name 'cluster_pb2'

I found there are a lot of unit tests in tensorflow repo, to understand tensorflow better and deeper, hopefully contribute a little some day, I thought running those unit test myself maybe a good idea for practice. while I was running into some exceptions throwed by session, I was trying to run session_test.py in http://ift.tt/2pZbncJ