def _kill_process(self, pid, sig=signal.SIGKILL):
        """Try to send signal to given process."""
        try:
            os.kill(pid, sig)
        except OSError as e:
            if e.errno == errno.ESRCH: # process itself returned and exited before killing
                logging.debug("Failure %s while killing process %s with signal %s: %s",
                              e.errno, pid, sig, e.strerror)
            else:
                logging.warning("Failure %s while killing process %s with signal %s: %s",
                                e.errno, pid, sig, e.strerror)
Try to send signal to given process.