Different error handling of kernel startup and restart

[rebornix]

Testing #10923

1. Create a new folder and a ipynb file with content print(123) in the first cell
2. Run the cell against a valid kernel (Python 3.6+)
3. Add an email.py file in the same folder
4. Restart the kernel

Now I got error message

Failed to start the Kernel. 
Cannot read properties of null (reading 'statusChanged'). 
View Jupyter [log](command:jupyter.viewOutput) for further details.

And in the Jupyter log it said

[E 10:34:35.419 NotebookApp] Error opening stream: HTTP 404: Not Found (Kernel does not exist: 4f479182-870f-4f57-a0b1-009e5853555e)

If we flip step 2 and 3, then we would get proper error message

Some of the following files found in the working directory may have prevented the Kernel from starting. Consider renaming them.
File(s): [~\email.py](file:///c%3A/Users/rebor/code/personal/notebooks/bugs/email.py?line=1) might need to be renamed.

[DonJayamanne]

Oh that's a weird error, never seen that before. Looks like Jupyter is in a broken state, we end up with a session but no kernel connection, very weird.
Guess we'll need to special case this.

@rebornix please could you provide the logs (I'd like to see the exact line when this fails). I'm assuming I know, but would like to be certain, as I cannot replicate this.

[rebornix]

@DonJayamanne the minified call stack is probably not easy to debug but here we go

[W 10:23:53.249 NotebookApp] delete /crash-jvsc-aff3bb37-f306-4172-a13a-10309f640e4c1dddf7a0-dad1-4fb7-a857-903eb60a80ff.ipynb
[I 10:23:56.250 NotebookApp] KernelRestarter: restarting kernel (1/5), new random ports
[I 10:23:59.270 NotebookApp] KernelRestarter: restarting kernel (2/5), new random ports
[I 10:24:02.280 NotebookApp] KernelRestarter: restarting kernel (3/5), new random ports
[I 10:24:05.302 NotebookApp] KernelRestarter: restarting kernel (4/5), new random ports
[W 10:24:08.308 NotebookApp] KernelRestarter: restart failed
[W 10:24:08.308 NotebookApp] Kernel cd644242-67e4-4c86-9070-e6c3bad2759e died, removing from map.
info 10:24:53.251: Error waiting for restart session: TypeError: Cannot read properties of null (reading 'statusChanged')
error 10:24:53.256: Restart failed c:\Users\rebor\code\personal\notebooks\bugs\crash.ipynb [TypeError: Cannot read properties of null (reading 'statusChanged')
	at waitForIdleOnSession (c:\Users\rebor\.vscode-insiders\extensions\ms-toolsai.jupyter-2022.7.1002101047\out\extension.node.js:2:1923258)
	at async w.createRestartSession (c:\Users\rebor\.vscode-insiders\extensions\ms-toolsai.jupyter-2022.7.1002101047\out\extension.node.js:2:2198963)]
[W 10:24:53.264 NotebookApp] Timeout waiting for kernel_info reply from cd644242-67e4-4c86-9070-e6c3bad2759e
[I 10:24:53.265 NotebookApp] Kernel shutdown: 1f907204-3600-471b-846d-8ee18149ea43
warn 10:24:53.590: Error occurred while trying to restart the kernel, options.disableUI=false [TypeError: Cannot read properties of null (reading 'statusChanged')
	at waitForIdleOnSession (c:\Users\rebor\.vscode-insiders\extensions\ms-toolsai.jupyter-2022.7.1002101047\out\extension.node.js:2:1923258)
	at async w.createRestartSession (c:\Users\rebor\.vscode-insiders\extensions\ms-toolsai.jupyter-2022.7.1002101047\out\extension.node.js:2:2198963)]
warn 10:24:53.592: Kernel Error, context = restart [TypeError: Cannot read properties of null (reading 'statusChanged')
	at waitForIdleOnSession (c:\Users\rebor\.vscode-insiders\extensions\ms-toolsai.jupyter-2022.7.1002101047\out\extension.node.js:2:1923258)
	at async w.createRestartSession (c:\Users\rebor\.vscode-insiders\extensions\ms-toolsai.jupyter-2022.7.1002101047\out\extension.node.js:2:2198963)]
info 10:24:53.597: Process Execution: > ~\.conda\envs\testenv\python.exe -c "import ipykernel"
> ~\.conda\envs\testenv\python.exe -c "import ipykernel"
[E 10:24:53.593 NotebookApp] Error opening stream: HTTP 404: Not Found (Kernel does not exist: cd644242-67e4-4c86-9070-e6c3bad2759e)
info 10:24:54.136: Dispose Kernel 'c:\Users\rebor\code\personal\notebooks\bugs\crash.ipynb' associated with 'c:\Users\rebor\code\personal\notebooks\bugs\crash.ipynb'
info 10:24:54.136: Cancel pending cells

[DonJayamanne]

Thanks, stack trace was very helpful, was able to find the exact spot where things failed