KF v1.6.0-rc.1 - MNIST E2E on Kubeflow on Vanilla k8s - TypeError: write() argument must be str, not <class 'bytes'>

Hello,

Testing KF v1.6.0-rc.1 Mnist E2E on vanilla K8s, I get an error executing tfjob_client.wait_for_job.

> from kubeflow.tfjob import TFJobClient
> tfjob_client = TFJobClient()
> tfjob_client.wait_for_job(train_name, namespace=namespace, watch=True)

Using KF v.1.5, it was successful but using v1.6.0-rc.1 an exception is raised.

> TypeError: write() argument must be str, not

Replacing previous iostream file version, the execution is successful.
/opt/conda/lib/python3.8/site-packages/ipykernel/iostream.py

Comparing the previous [version ](https://github.com/ipython/ipykernel/blob/91550b37f78cb2db6590f591b3eeacd653fba9b4/ipykernel/iostream.py) with the latest [version](https://github.com/ipython/ipykernel/blob/724753a185b0954f0e662c226b86dc8146c62bcb/ipykernel/iostream.py)

The following code seems to cause the issue.

> if not isinstance(string, str):
> raise TypeError(f"write() argument must be str, not {type(string)}")

I don't know how to fix the issue but my current workaround is to replace the iostream.py file with the previous version.

Thank you

Reproduce the MNIST E2E failure at tfjob_client.wait_for_job(..., watch=True) on Kubeflow v1.6.0-rc.1. Compare /opt/conda/lib/python3.8/site-packages/ipykernel/iostream.py with the linked previous and latest versions, then verify that the TypeError no longer occurs without replacing the file manually.

Written by the indexing model from the issue text.