def send_signal(self, signum):
        """Send the signal *signum* to the child.

        On Windows, SIGTERM, SIGKILL and SIGINT are emulated using
        TerminateProcess(). This will cause the child to exit unconditionally
        with status 1. No other signals can be sent on Windows.
        """
        if self._process is None:
            raise RuntimeError('no child process')
        self._process.kill(signum)