tests: use Python 3.6 APIs

Author: michalc

test.py

@@ -1780,27 +1780,30 @@ async def func():
             return 42
 
         memoized = MemoizedMutex(func)
-        task1 = asyncio.create_task(memoized())
-        task2 = asyncio.create_task(memoized())
-        task3 = asyncio.create_task(memoized())
+        loop = asyncio.get_event_loop()
+
+        task1 = loop.create_task(memoized())
+        task2 = loop.create_task(memoized())
+        task3 = loop.create_task(memoized())
 
         self.assertEqual(await task1, 42)
         self.assertEqual(await task2, 42)
         self.assertEqual(await task3, 42)
 
-
     @async_test
     async def test_usage_after_resolve(self):
         async def func():
             await asyncio.sleep(0)
             return 42
 
         memoized = MemoizedMutex(func)
-        task1 = asyncio.create_task(memoized())
+        loop = asyncio.get_event_loop()
+
+        task1 = loop.create_task(memoized())
         self.assertEqual(await task1, 42)
 
-        task2 = asyncio.create_task(memoized())
-        task3 = asyncio.create_task(memoized())
+        task2 = loop.create_task(memoized())
+        task3 = loop.create_task(memoized())
         self.assertEqual(await task2, 42)
         self.assertEqual(await task3, 42)