bpo-38785: Prevent asyncio from crashing (GH-17144)

if parent `__init__` is not called from a constructor of object derived from `asyncio.Future`



https://bugs.python.org/issue38785

Lib/asyncio/futures.py

@@ -115,7 +115,10 @@ class Future:
 
     def get_loop(self):
         """Return the event loop the Future is bound to."""
-        return self._loop
+        loop = self._loop
+        if loop is None:
+            raise RuntimeError("Future object is not initialized.")
+        return loop
 
     def cancel(self):
         """Cancel the future and schedule callbacks.