refer to https://www.terraform.io/docs/commands/plan.html
        :param detailed_exitcode: Return a detailed exit code when the command exits.
        :param dir_or_plan: relative path to plan/folder
        :param kwargs: options
        :return: ret_code, stdout, stderr

def plan(self, dir_or_plan=None, detailed_exitcode=IsFlagged, **kwargs):
        """
        refer to https://www.terraform.io/docs/commands/plan.html
        :param detailed_exitcode: Return a detailed exit code when the command exits.
        :param dir_or_plan: relative path to plan/folder
        :param kwargs: options
        :return: ret_code, stdout, stderr
        """
        options = kwargs
        options['detailed_exitcode'] = detailed_exitcode
        options = self._generate_default_options(options)
        args = self._generate_default_args(dir_or_plan)
        return self.cmd('plan', *args, **options)