windows: set exceptions on pending futures

Author: hartytp

qasync/_windows.py

@@ -41,8 +41,10 @@ def _process_events(self, events):
             try:
                 self._logger.debug('Invoking event callback {}'.format(callback))
                 value = callback(transferred, key, ov)
-            except OSError:
+            except OSError as e:
                 self._logger.debug('Event callback failed', exc_info=sys.exc_info())
+                if not f.done():
+                    f.set_exception(e)
             else:
                 if not f.cancelled():
                     f.set_result(value)