On Ubuntu 16.04, which has Python 3.5.2, this raised `TypeError: descriptor '__subclasses__' of 'type' object needs an argument` (https://github.com/python/typing/issues/266). Signed-off-by: Anders Kaseorg <andersk@mit.edu>
On Ubuntu 16.04, which has Python 3.5.2, `apns2.client` failed to import, because `typing.Deque` was not added until Python 3.5.4. Fixes #88. Signed-off-by: Anders Kaseorg <andersk@mit.edu>