Properly reexec gunicorn's Arbiter

arbiter.py

    def reexec(self):
        """\
        Relaunch the master and workers.
        """
        self.kill_workers(signal.SIGQUIT)

        fds = [l.fileno() for l in self.LISTENERS]
        os.environ['GUNICORN_FD'] = ",".join([str(fd) for fd in fds])

        os.chdir(self.START_CTX['cwd'])
        self.cfg.pre_exec(self)

        # close all file descriptors except bound sockets
        util.closerange(3, fds[0])
        util.closerange(fds[-1] + 1, util.get_maxfd())

        os.execvpe(self.START_CTX[0], self.START_CTX['args'], os.environ)