import asyncio
import unittest

loop = asyncio.get_event_loop()
global_future = loop.create_future()
closing = loop.create_future()


async def push_errors_to_main_task(exc):
    global_future.set_exception(exc)
    print("Error pushed to main task. Backoff for some time...")
    try:
        await asyncio.sleep(0.2, loop=loop)
    except BaseException as exc:
        print("Sleep failed", repr(exc))
        raise


@asyncio.coroutine
def coordination():
    while not closing.done():
        print("Coordinate")
        yield from asyncio.sleep(1, loop=loop)
        try:
            raise ValueError()
        except Exception as exc:
            print("Error occured")
            yield from push_errors_to_main_task(exc)
            continue


class TestOne(unittest.TestCase):

    async def main(self):
        # Create background task that is suspendable in case of error
        task = loop.create_task(coordination())

        with self.assertRaises(ValueError):
            await global_future

        # Teardown like
        print("Graceful stop")
        closing.set_result(None)
        await task
        print("Finished")

    def test_one(self):
        loop.run_until_complete(self.main())


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