@@ -149,7 +149,7 @@ class ParallelSchedulingTest(unittest.TestCase):
             UnpicklableExceptionTask().complete()
         except Exception as e:
             ex = e
-        self.assertRaises(pickle.PicklingError, pickle.dumps, ex)
+        self.assertRaises(Exception, pickle.dumps, ex)
 
         # verify this can run async
         self.w.add(UnpicklableExceptionTask(), multiprocess=True)
# -*- coding: utf-8 -*-
#
# Copyright 2012-2015 Spotify AB
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

import contextlib
import gc
import os
import pickle
import time
from helpers import unittest

import luigi
import mock
import psutil
from luigi.worker import Worker


def running_children():
    children = set()
    process = psutil.Process(os.getpid())
    for child in process.children():
        if child.is_running():
            children.add(child.pid)
    return children


@contextlib.contextmanager
def pause_gc():
    if not gc.isenabled():
        yield
    try:
        gc.disable()
        yield
    finally:
        gc.enable()


class SlowCompleteWrapper(luigi.WrapperTask):

    def requires(self):
        return [SlowCompleteTask(i) for i in range(4)]


class SlowCompleteTask(luigi.Task):
    n = luigi.IntParameter()

    def complete(self):
        time.sleep(0.1)
        return True


class OverlappingSelfDependenciesTask(luigi.Task):
    n = luigi.IntParameter()
    k = luigi.IntParameter()

    def complete(self):
        return self.n < self.k or self.k == 0

    def requires(self):
        return [OverlappingSelfDependenciesTask(self.n - 1, k) for k in range(self.k + 1)]


class ExceptionCompleteTask(luigi.Task):

    def complete(self):
        assert False


class ExceptionRequiresTask(luigi.Task):

    def requires(self):
        assert False


class UnpicklableExceptionTask(luigi.Task):

    def complete(self):
        class UnpicklableException(Exception):
            pass
        raise UnpicklableException()


class ParallelSchedulingTest(unittest.TestCase):

    def setUp(self):
        self.sch = mock.Mock()
        self.w = Worker(scheduler=self.sch, worker_id='x')

    def added_tasks(self, status):
        return [kw['task_id'] for args, kw in self.sch.add_task.call_args_list if kw['status'] == status]

    def test_children_terminated(self):
        before_children = running_children()
        with pause_gc():
            self.w.add(
                OverlappingSelfDependenciesTask(5, 2),
                multiprocess=True,
            )
            self.assertLessEqual(running_children(), before_children)

    def test_multiprocess_scheduling_with_overlapping_dependencies(self):
        self.w.add(OverlappingSelfDependenciesTask(5, 2), True)
        self.assertEqual(15, self.sch.add_task.call_count)
        self.assertEqual(set((
            OverlappingSelfDependenciesTask(n=1, k=1).task_id,
            OverlappingSelfDependenciesTask(n=2, k=1).task_id,
            OverlappingSelfDependenciesTask(n=2, k=2).task_id,
            OverlappingSelfDependenciesTask(n=3, k=1).task_id,
            OverlappingSelfDependenciesTask(n=3, k=2).task_id,
            OverlappingSelfDependenciesTask(n=4, k=1).task_id,
            OverlappingSelfDependenciesTask(n=4, k=2).task_id,
            OverlappingSelfDependenciesTask(n=5, k=2).task_id,
        )), set(self.added_tasks('PENDING')))
        self.assertEqual(set((
            OverlappingSelfDependenciesTask(n=0, k=0).task_id,
            OverlappingSelfDependenciesTask(n=0, k=1).task_id,
            OverlappingSelfDependenciesTask(n=1, k=0).task_id,
            OverlappingSelfDependenciesTask(n=1, k=2).task_id,
            OverlappingSelfDependenciesTask(n=2, k=0).task_id,
            OverlappingSelfDependenciesTask(n=3, k=0).task_id,
            OverlappingSelfDependenciesTask(n=4, k=0).task_id,
        )), set(self.added_tasks('DONE')))

    @mock.patch('luigi.notifications.send_error_email')
    def test_raise_exception_in_complete(self, send):
        self.w.add(ExceptionCompleteTask(), multiprocess=True)
        send.check_called_once()
        self.assertEqual(0, self.sch.add_task.call_count)
        self.assertTrue('assert False' in send.call_args[0][1])

    @mock.patch('luigi.notifications.send_error_email')
    def test_raise_unpicklable_exception_in_complete(self, send):
        # verify exception can't be pickled
        self.assertRaises(Exception, UnpicklableExceptionTask().complete)
        try:
            UnpicklableExceptionTask().complete()
        except Exception as e:
            ex = e
        self.assertRaises(pickle.PicklingError, pickle.dumps, ex)

        # verify this can run async
        self.w.add(UnpicklableExceptionTask(), multiprocess=True)
        send.check_called_once()
        self.assertEqual(0, self.sch.add_task.call_count)
        self.assertTrue('raise UnpicklableException()' in send.call_args[0][1])

    @mock.patch('luigi.notifications.send_error_email')
    def test_raise_exception_in_requires(self, send):
        self.w.add(ExceptionRequiresTask(), multiprocess=True)
        send.check_called_once()
        self.assertEqual(0, self.sch.add_task.call_count)


if __name__ == '__main__':
    unittest.main()

I remember you understood this part the best @daveFNbuck, does this code change look sensible to you?