Fix #507: fix asyncio issues (PR #531)

How fixed: use previous ascynio version.

Calina: Asyncio has some known issues, per their changelog. Namely issues with fixture handling etc., which I believe causes the warnings and test skips in our runs. They recommend using the previous version until they are fixed. It is also why my setup didn't spew up any warnings, my asyncio version was 21.1.

https://pytest-asyncio.readthedocs.io/en/latest/reference/changelog.html

setup.py

@@ -26,7 +26,7 @@
     "pyarrow",
     "pylint",
     "pytest",
-    "pytest-asyncio",
+    "pytest-asyncio==0.21.1",
     "pytest-env",
     "pyyaml",
     "requests",