code: function getAvailableNPMVersions () {
    return new Promise((resolve, reject) => {
      exec('npm view npm versions --json', (err, stdout) => {
        if (err) {
          let error = 'We could not show latest available versions. Try running this script again '
          error += 'with the version you want to install (npm-windows-upgrade --npm-version 3.0.0)'
          return reject(error)
        }
  
        resolve(JSON.parse(stdout))
      })
    })
  }
docs: Fetches the published versions of npm from the npm registry
  @return {Promise.<versions[]>} - Array of the available versions