Latest version break IPyWidgets

[DonJayamanne]

IPyKernel Version: 6.19.0
Install Jupyter and ipywidgets
Run a notebook with the following code

import ipywidgets as widgets
widgets.IntSlider()

Slider is not renderered
Here is the error message

A Jupyter widget could not be displayed because the widget state could not be found. 
This could happen if the kernel storing the widget is no longer available, or if the widget state was not saved in the notebook. 
You may be able to create the widget by running the appropriate cells.

[maartenbreddels]

I tried reproducing this, but I cannot. I did:

python -m venv clean-env 
source clean-env/bin/activate
pip install ipywidgets notebook jupyterlab

Confirmed I had ipykernel 6.19.0 and ran your code snippet in lab and classic notebook, and it works.

[martinRenou]

I can reproduce in JupyterLab. It seems that it fails to open the comm.

[maartenbreddels]

Yes, I do too. The reason it worked for me, is because I had my notebook in the ipykernel git root directory, so that the Python runtime picked up the ipykernel git branch I was in, which was 5f42999 (the state of branch #1049 before I pushed).
I'll check which commit broke it.

[maartenbreddels]

Seems fee98e5 is the issue. I'll make a fix.