Modify error string "Could not load unit test config from launch.json" to be more specific about which fields are missing #14381
Description
I had a lot of trouble getting "justMyCode" = false to work because I kept getting "Could not load unit test config from launch.json". This was despite that fact that launch configs showed up fine in the debug configuration dropdown and that debugging worked.
The issue was a missing "version" attribute in launch.json but I had to read the source to find this. I'm posting an issue hoping that the error message is improved or maybe it helps somebody else, this error bugged me for quite a while.
The following message is seen in "Python" output tab:
Error 2020-10-13 02:54:01: could not get debug config [Error: malformed launch.json
at _.readAllDebugConfigs (/home/leonard/.vscode-oss/extensions/ms-python.python-2020.9.112786/out/client/extension.js:56:931824)
at runMicrotasks (<anonymous>)
at processTicksAndRejections (internal/process/task_queues.js:94:5)
at async _.readDebugConfig (/home/leonard/.vscode-oss/extensions/ms-python.python-2020.9.112786/out/client/extension.js:56:932663)
at async _.getLaunchArgs (/home/leonard/.vscode-oss/extensions/ms-python.python-2020.9.112786/out/client/extension.js:56:932363)
at async _.launchDebugger (/home/leonard/.vscode-oss/extensions/ms-python.python-2020.9.112786/out/client/extension.js:56:931326)
at async h.runTest (/home/leonard/.vscode-oss/extensions/ms-python.python-2020.9.112786/out/client/extension.js:56:1036991)
at async c.runTestImpl (/home/leonard/.vscode-oss/extensions/ms-python.python-2020.9.112786/out/client/extension.js:56:1034988)]
Exception is thrown from here: https://github.com/microsoft/vscode-python/blob/main/src/client/testing/common/debugLauncher.ts#L58
You can probably reproduce this by removing "version" from launch.json.