When a previous call to poll() has already seen the process status,

wait() should not call waitpid() again.

Should be backported to 2.2.4.

Lib/popen2.py

@@ -83,6 +83,7 @@ class Popen3:
 
     def wait(self):
         """Wait for and return the exit status of the child process."""
+        if self.sts < 0:
             pid, sts = os.waitpid(self.pid, 0)
             if pid == self.pid:
                 self.sts = sts