Return status code after timeout: usually this will be None, as we are

returning now, except if we raced with another thread that set it just after
our timeout expired.

Author: duaneg

Lib/multiprocessing/popen_forkserver.py

@@ -65,7 +65,7 @@ def poll(self, flag=os.WNOHANG):
             from multiprocessing.connection import wait
             timeout = 0 if flag == os.WNOHANG else None
             if not wait([self.sentinel], timeout):
-                return None
+                return self.returncode
 
             with self._lock:
                 if self.returncode is None: