[fix] Use asyncio.ensure_future() instead of async() which disapear from Py 3.7

src/sakia/services/network.py

@@ -290,7 +290,7 @@ class NetworkService(QObject):
     def run_ws2p_check(self):
         if not self._ws2p_heads_refreshing:
             self._ws2p_heads_refreshing = True
-            asyncio.async(self.check_ws2p_heads())
+            asyncio.ensure_future(self.check_ws2p_heads())
 
     async def check_ws2p_heads(self):
         await asyncio.sleep(5)