When attempting to build in the core/distributed_runtime module using:
$ bazel build -c opt 
   //tensorflow/core/distributed_runtime/rpc:grpc_tensorflow_server
We get the following error:
ERROR: error loading package 'tensorflow/core/distributed_runtime/rpc': 
Extension file not found. Unable to load package for
   '//google/protobuf:protobuf.bzl': BUILD file not found on package path.
INFO: Elapsed time: 0.097s
Are there additional steps required (and not mentioned in the README.md) ?
 
     
    