Event loop stalls in network test

[mhsmith]

Describe the bug

[@mhsmith] The test app from beeware/rubicon-java#49 works on Android (after merging beeware/toga#2481), but it doesn't work on macOS – it stops at the first network connection. Is there something wrong with the Cocoa event loop implementation?

[@freakboy3742] Interesting... asyncio.ensure_future(self.say_sleep_works()) stalls after the sleep, but self.loop.create_task(self.say_sleep_works()) does work. My guess is that there is something odd going on with asyncio.get_event_loop(); more investigation is definitely required.

Environment

• Operating System: macOS
• Python version: 3.8
• Software versions:
  • Rubicon: 0.4.7