Python 2.7 doesn't seem to be affected by this issue. Extract of Popen.__init__:

        try:
            self._execute_child(args, executable, preexec_fn, close_fds,
                                cwd, env, universal_newlines,
                                startupinfo, creationflags, shell, to_close,
                                p2cread, p2cwrite,
                                c2pread, c2pwrite,
                                errread, errwrite)
        except Exception:
            # Preserve original exception in case os.close raises.
            exc_type, exc_value, exc_trace = sys.exc_info()

            for fd in to_close:
                try:
                    if mswindows:
                        fd.Close()
                    else:
                        os.close(fd)
                except EnvironmentError:
                    pass

On Windows, fd.Close() is always used.