Use asyncio.ensure_future() instead of asyncio.async() with conservative approach to support Python < 3.4.4. Fixes https://github.com/GNS3/gns3-gui/issues/2566

gns3server/compute/base_manager.py

@@ -30,6 +30,7 @@ log = logging.getLogger(__name__)
 
 from uuid import UUID, uuid4
 from gns3server.utils.interfaces import is_interface_up
+from gns3server.utils.asyncio import asyncio_ensure_future
 from ..config import Config
 from ..utils.asyncio import wait_run_in_executor
 from ..utils import force_unix_path
@@ -127,7 +128,7 @@ class BaseManager:
 
         tasks = []
         for node_id in self._nodes.keys():
-            tasks.append(asyncio.async(self.close_node(node_id)))
+            tasks.append(asyncio_ensure_future(self.close_node(node_id)))
 
         if tasks:
             done, _ = yield from asyncio.wait(tasks)