message: Fix Bazel fetch commands by binding python_headers
diff: @@ -520,6 +520,13 @@ def _com_google_protobuf():
  actual = "@com_google_protobuf_cc//:protoc",
  )
  + # Needed for `bazel fetch` to work with @com_google_protobuf
  + # https://github.com/google/protobuf/blob/v3.6.1/util/python/BUILD#L6-L9
  + native.bind(
  + name = "python_headers",
  + actual = "@com_google_protobuf//util/python:python_headers",
  + )
  +
  def _com_github_grpc_grpc():
  _repository_impl("com_github_grpc_grpc")
  