解决新版 hexo 无法部署到 heroku 的错误

把 hexo 更新到最新版（3.9.0）之后，在运行 hexo deploy --generate 发现无法部署，控制台提示如下

!     ERROR: Application not supported by 'heroku/nodejs' buildpack
!     
!     The 'heroku/nodejs' buildpack is set on this application, but was
!     unable to detect a Node.js codebase.
!         
!     A Node.js app on Heroku requires a 'package.json' at the root of
!     the directory structure.
!     
!     If you are trying to deploy a Node.js application, ensure that this
!     file is present at the top level directory. This directory has the
!     following files:
!     
!     index.php
!     Procfile
!     public/
!         
!     If you are trying to deploy an application written in another
!     language, you need to change the list of buildpacks set on your
!     Heroku app using the 'heroku buildpacks' command.
!         
!     For more information, refer to the following documentation:
!     https://devcenter.heroku.com/articles/buildpacks
!     https://devcenter.heroku.com/articles/nodejs-support#activation
      More info: https://devcenter.heroku.com/articles/buildpacks#detection-failure
!     Push failed

然后看了一下 .deploy_heroku 文件夹里的 Procfile 文件，这是已经从原来的 nodeje 项目变成了 nginx 的了？？这跟之前运行时环境不一样，造成了部署无法成功。

看了控制台出现的那两链接，以及 stackoverflow 的回答，需要把原来的 buildpack 给删掉，之后再部署就行了。那么就好办了

heroku buildpacks:remove heroku/nodejs -a APP
hexo deploy --generate

结束。