@pytest.fixture(scope='function')
def map_that_never_finishes(never_returns):
    m = htmap.map(never_returns, [None])
    (yield m)
    m.remove()
@pytest.fixture(scope='function')
def map_that_never_finishes(never_returns):
    m = htmap.map(never_returns, [None])
    (yield m)
    m.remove()