async chooseVersion () {
    if (!this.options.npmVersion) {
      const availableVersions = await versions.getAvailableNPMVersions()
      const versionList = [{
        type: 'list',
        name: 'version',
        message: 'Which version do you want to install?',
        choices: availableVersions.reverse()
      }]

      this.options.npmVersion = await inquirer.prompt(versionList)
        .then(answer => answer.version)
    }

    if (this.options.npmVersion === 'latest') {
      this.options.npmVersion = await versions.getLatestNPMVersion()
    }
  }
Executes the upgrader's "let's have the user choose a version" logic