Always set _closed future in StdoutWriterProtocol.connection_lost

Otherwise when the stdout stream is closed wait_closed will hang
forvever.

See #24 for
discussion about the exact intended behavior or WriterProtocol in this
case.

QubesOS/qubes-issues#9779

Author: HW42

splitgpg2/stdiostream.py

@@ -43,16 +43,16 @@ def resume_writing(self) -> None:
 
     def connection_lost(self, exc: Optional[BaseException]) -> None:
         self._connection_lost = True
+
         # Wake up the writer(s) if currently paused.
-        if not self._paused:
-            return
+        if self._paused:
+            for waiter in self._drain_waiters:
+                if not waiter.done():
+                    if exc is None:
+                        waiter.set_result(None)
+                    else:
+                        waiter.set_exception(exc)
 
-        for waiter in self._drain_waiters:
-            if not waiter.done():
-                if exc is None:
-                    waiter.set_result(None)
-                else:
-                    waiter.set_exception(exc)
         if not self._closed.done():
             if exc is None:
                 self._closed.set_result(None)