'Send a command and block until it finishes.
This method will send a command to the cmd-runner process
to run.  It will block until the cmd-runner process is
finished executing the command and sends back a status
response.'

def cmd(self, *cmd):

    self.send_cmd(*cmd)
    result = self._popen.stdout.readline().strip()
    if (result != 'OK'):
        raise RuntimeError(("Error    from    command    '%s':    %s" % (cmd, result)))
