pytest asyncio 0.15.1 is broken too (#498)

Author: escapewindow

tox.ini

@@ -28,7 +28,7 @@ deps =
     mock
     pytest
     # https://github.com/pytest-dev/pytest-asyncio/issues/209
-    pytest-asyncio!=0.15.0
+    pytest-asyncio<0.15
     pytest-cov
     pytest-mock
     pytest-random-order