Fix LocalExecutor crash on non-picklable exceptions (e.g. httpx.HTTPStatusError)

[Pranaykarvi]

Closes #64476

When LocalExecutor runs a task in a subprocess, exceptions are passed back via multiprocessing.Queue using pickle. Some exceptions like httpx.HTTPStatusError are not pickle-safe, causing:

TypeError: HTTPStatusError.__init__() missing 2 required keyword-only arguments: 'request' and 'response'

This crashes the scheduler loop and takes down the entire scheduler pod.

Root Cause

Raw exception objects were placed directly onto the result queue:

output.put((key, TaskInstanceState.FAILED, e))

Fix

Wrap the exception in a plain Exception before queuing:

safe_exc = Exception(f"{type(e).__name__}: {str(e)}\n{traceback.format_exc()}")
output.put((key, TaskInstanceState.FAILED, safe_exc))

Applied to both ExecuteTask and ExecuteCallback branches.

Impact

• Scheduler no longer crashes on non-picklable exceptions
• Full debugging info preserved
• Minimal change, no other executor behaviour affected

[eladkal]

@Pranaykarvi please explain how you verified the issue present only in LocalExecutor?