Pin pytest-asyncio version

[jrbourbeau]

Checking whether or not the Travis CI failures in #4204 are related to the changes there

[jrbourbeau]

In its latest release, pytest-asyncio began modifying the default asyncio event_loop_policy which broke tests here as we need to explicitly set our event loop policy

distributed/distributed/utils.py

Line 1237 in cee4e3c

asyncio.set_event_loop_policy(AnyThreadEventLoopPolicy())

There is a discussion of how to proceed on the pytest-asyncio side (xref pytest-dev/pytest-asyncio#168) but for now we should just set an upper limit on our allowed version of pytest-asycnio

[jrbourbeau]

Tests on Windows (mostly) pass 🎉 I've been test_tls_specific fail before on master (xref https://github.com/dask/distributed/runs/1332842736#step:8:116) and opened up an issue for tracking the failure (#4215)

[TomAugspurger]

Thanks.

We'll want to backport this to 2.30.x as well once it's merged.

[jrbourbeau]

Merging as the two test failures are known flaky tests