Add compatibility with Notebook 4.2 and add an error message for Notebook 4.3.0
Add compatibility with Notebook 4.2 and add an error message for Notebook 4.3.0

jupyter/jupyter-js-services,jupyterlab/services,jupyterlab/services,jupyter/jupyter-js-services,jupyter/jupyter-js-services,jupyterlab/services,jupyterlab/services,jupyter/jupyter-js-services