import asyncio
import unittest

async def it(raise_, ignore=True):
    yield 1
    if not ignore:
        await asyncio.sleep(0.01)

    try:
        raise ValueError('test2') from raise_
    except Exception:
        import traceback
        traceback.print_exc()
        if ignore:
            pass
        else:
            raise
    await asyncio.sleep(0.1)
    yield 2


class MyTest(unittest.TestCase):
    def test(self):
        try:
            raise ValueError('testerror')
        except ValueError as e:
            exc = e
        async def task1():
            with self.assertRaises(ValueError):
                async for i in it(exc, False):
                    print("task1: ", i)


        async def task2():
            async for i in it(exc, True):
                print("task2: ", i)


        async def main():
            t1 = asyncio.ensure_future(task1())
            t2 = asyncio.ensure_future(task2())
            await t1
            await t2
        asyncio.get_event_loop().run_until_complete(main())

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