How to use the buntstift.exit function in buntstift

const packageJson = require('../package.json');

/* eslint-disable no-sync */
updateNotifier({
  packageName: packageJson.name,
  packageVersion: packageJson.version
}).notify();

if (!fs.existsSync(path.join(process.cwd(), 'node_modules', 'roboter'))) {
  buntstift.error('roboter is not installed locally.');
  buntstift.newLine();
  buntstift.info('Please run the following command:');
  buntstift.newLine();
  buntstift.info('  npm install roboter --save-dev --save-exact');
  buntstift.exit(1);
}

const localRoboterPackageJson = require(path.join(
  process.cwd(), 'node_modules', 'roboter', 'package.json'));

if (semver.gt(localRoboterPackageJson.version, packageJson.version)) {
  buntstift.error('The roboter runner is too old.');
  buntstift.newLine();
  buntstift.info('Please run the following command:');
  buntstift.newLine();
  buntstift.info('  npm install -g roboter');
  buntstift.exit(1);
}

const gulp = path.join(process.cwd(), 'node_modules', '.bin', 'gulp');

const configurationFile = minimist(process.argv.slice(2), {
  string: 'file',
  default: 'roboter.js'
}).file || 'roboter.js';

const configurationFileWithPath = path.join(process.cwd(), configurationFile);

if (!fs.existsSync(configurationFileWithPath)) {
  buntstift.error(`${configurationFile} is missing.`);
  buntstift.exit(1);
}

const args = process.argv.slice(2).join(' ');

buntstift.exit(shell.exec(
  `${gulp} --gulpfile ${configurationFileWithPath} --color true ${args}`).code);
/* eslint-enable no-sync */