Executes a simple external command and return its exit status
        
        :param stderr: where to put stderr
        :return: return code of command

def get_return_code(self, stderr=STDOUT):
        """Executes a simple external command and return its exit status
        
        :param stderr: where to put stderr
        :return: return code of command
        """
        args = shlex.split(self.cmd)
        return call(args, stdout=PIPE, stderr=stderr)