Scaler's Future.done() does not work as expected

[rafa-be]

When checking a Scaler's Future.done() status, without calling Future.result() or Future.add_done_callback(), the call never returns True:

f = c.submit(round, 10.6)

while not f.done():  # will loop forever
    pass

However, adding a callback prevents the issue:

f = c.submit(round, 10.6)
f.add_done_callback(print)

while not f.done():  # will not block indefinitely
    pass