I've been following the instruction at https://cloud.google.com/tpu/docs/custom-setup
and now I'm trying to run a tiny example from https://cloud.google.com/tpu/docs/quickstart
But it hangs on sess.run(tpu.initialize_system())
I suspect that it can't access the TPU network endpoint, even though "gcloud beta compute tpus list" returns status "READY".