Notification overload when installing ipykernel

[Tyriar]

Testing microsoft/vscode#114969

I pressed install and I got 3 notifications and the original showed up again. This was so many notifications some were hidden immediately:

Additionally, the connecting to kernel notification never ends 😱

[Tyriar]

I think this happened because pip wasn't available, the extension should call python -m pip --version to verify and give a useful error that offers to install pip.