bpo-38978: Implement __class_getitem__ for asyncio objects (GH-17491)



https://bugs.python.org/issue38978
diff --git a/Lib/asyncio/futures.py b/Lib/asyncio/futures.py
index 9afda22..a3cf379 100644
--- a/Lib/asyncio/futures.py
+++ b/Lib/asyncio/futures.py
@@ -103,6 +103,9 @@
             context['source_traceback'] = self._source_traceback
         self._loop.call_exception_handler(context)
 
+    def __class_getitem__(cls, type):
+        return cls
+
     @property
     def _log_traceback(self):
         return self.__log_traceback