Python CatchableProcess: Catch exceptions in spawned processes

catchableprocess.py

from multiprocessing import Process

class CatchableProcess(Process):
    def __init__(self, target, args=[], kwargs=dict()):
        from multiprocessing import Queue
        self.error = Queue(1)
        self.result = Queue(1)

        def wrapper(target, args, kwargs):
            try:
                res = target(*args, **kwargs)
                self.result.put(res)
            except Exception as e:
                self.error.put(e)
                raise

        super(CatchableProcess, self).__init__(target=wrapper,
                                               kwargs=dict(
                                                   target=target,
                                                   args=args,
                                                   kwargs=kwargs
                                               ))

    def join(self, timeout=None):
        super(CatchableProcess, self).join(timeout)

        if not self.error.empty():
            raise self.error.get()

        if not self.result.empty():
            return self.result.get()
        else:
            return None

test.py

import unittest
from catchableprocess import CatchableProcess

class CatchableProcessTest(unittest.TestCase):
    def test_catchable_process(self):
        def dummy():
            raise Exception('should be catched')

        p = CatchableProcess(target=dummy)
        p.start()
        self.assertRaises(p.join)

    def test_normal_process(self):
        def dummy():
            return 10

        p = CatchableProcess(target=dummy)
        p.start()
        self.assertEqual(p.join(), 10)

    def test_normal_process_with_none_response(self):
        def dummy(): pass

        p = CatchableProcess(target=dummy)
        p.start()
        self.assertIsNone(p.join())

    def test_get_pid(self):
        def dummy(): pass
        p = CatchableProcess(target=dummy)
        p.start()
        self.assertIsInstance(p.pid, int)
        p.join()

    def test_terminate(self):
        def dummy():
            import time
            time.sleep(1)
            raise Exception('should be killed long before')

        p = CatchableProcess(target=dummy)
        p.start()
        p.terminate()
        p.join()