Python debugger throwing non-actionable error if Python is not in Path

[sivakku]

From stack overflow article: https://stackoverflow.com/questions/69818514/cloud-code-kubernetes-spawn-python-enoent-error-in-vs-code-when-attaching-a-debu

From cloud-code-vscode-internal created by quoctruong: GoogleCloudPlatform/cloud-code-vscode-internal#5848

We are missing a which statement here:
https://github.com/GoogleCloudPlatform/cloud-code-vscode-internal/blob/dd72c6c7a13a0d48379f965712597fa29153da23/src/kubernetes/src/debuggers/python_debug_agent.ts#L91

Because of this, users can get a cryptic ENOENT spawn Python error.