code: function exec(cmd, args, opts) {
    console.log(`Running command: ${cmd} ${args.join(' ')}`);
    const cp = childProcessSpawn(cmd, args, opts);
  
    cp.stdout.on('data', data => log(data));
    cp.stderr.on('data', data => log(data));
  
    return new Promise((resolve, reject) => {
      cp.on('error', err => reject(log(err)));
      cp.on('exit', code => resolve(code));
    });
  }
docs: Spawns a child_process and returns a promise.
  @name exec