callback转Promise

环境：  nodejs - v6.2.0

 const fs = require('fs');

 let Promise = require('bluebird');

 let readSync = function(filePath) {
   return new Promise(function(resolve, reject) {
       fs.unlink(filePath, (err) => {
         if(err) return reject(err);
         return resolve();
       })
   })
 }

 readSync('log').then(function(data) {
   console.log('OKKKKK');
 }).catch(function(err) {
   console.log(err || 'errror!!');
 })