Handle if async generators are GCed from another thread.

1st1 · 1st1 · commit f5ab2bb4d93c · 2016-10-18T11:41:58.000-04:00
_asyncgen_finalizer_hook should wake up the loop in case it was
called from another thread.
diff --git a/asyncio/base_events.py b/asyncio/base_events.py
@@ -351,6 +351,9 @@ def _asyncgen_finalizer_hook(self, agen):
         self._asyncgens.discard(agen)
         if not self.is_closed():
             self.create_task(agen.aclose())
+            # Wake up the loop if the finalizer was called from
+            # a different thread.
+            self._write_to_self()
 
     def _asyncgen_firstiter_hook(self, agen):
         if self._asyncgens_shutdown_called:
