fix sniffio-less asyncio detection on 3.6.x

diff --git a/dns/asyncbackend.py b/dns/asyncbackend.py
index f028417c971474b6f10286753c89e0e487325116..9582a6f8120e5f10336411648cd3ce989681ae91 100644 (file)
--- a/dns/asyncbackend.py
+++ b/dns/asyncbackend.py
@@ -70,6 +70,7 @@ def sniff():
             # we have to check current_task on 3.6
             if not asyncio.Task.current_task():
                 raise AsyncLibraryNotFoundError('no async library detected')
+            return 'asyncio'
 
 
 def get_default_backend():