Note: thread error to pass back to the main

[Suke0811]

Asyncio, threadpoolexecutor can do this well (Python threading needs a hack).
https://superfastpython.com/threadpoolexecutor-exception-handling/#Exception_Handling_in_Callbacks

The best is to use a callback like this

def exception_call(fut):
    fut.result()
[fut.add_done_callback(exception_call) for fut in self.futs]

The callback is always called individually regardless of success or exceptions.
fut.result() will re-create the exception from the thread in the main.
fut.exception() can alternatively show no traceback, but just exception info