这个错误发生的原因是因为Heroku跑过我的生产环境。因为CKEditor正在一个新的环境中设置，它会尝试编写一堆文件。因为Heroku是一个只读文件系统，因此中止这个过程。为了绕过此错误：

The reason this error occured was because Heroku ran on my production environment. Because CKEditor is being set up on a new environment, it attempts to write a bunch of files. Because Heroku is a read-only file system it aborts this process. In order to bypass this error :

在本地计算机上执行以下操作：

On your local machine, perform this :

rails s -e production

查看您的网站，CKeditor会将这些文件写入生产环境。

View your site, CKeditor will write those files for production env.

git add .
git commit -m "added files to Production for Heroku"
git push heroku master

应该现在！