Use asyncio.WindowsSelectorEventLoopPolicy for 3.8+

https://twistedmatrix.com/trac/ticket/9766

Author: altendky

pytest_twisted.py

@@ -272,6 +272,12 @@ def init_qt5_reactor():
 
 
 def init_asyncio_reactor():
+    if sys.version_info >= (3, 8):
+        # If twisted releases a fix/workaround we can check that version too
+        # https://twistedmatrix.com/trac/ticket/9766
+        selector_policy = asyncio.WindowsSelectorEventLoopPolicy()
+        asyncio.set_event_loop_policy(selector_policy)
+    
     from twisted.internet import asyncioreactor
 
     _install_reactor(