You must chmod 755 concrete/libraries/3rdparty/htmldiff.py and disable PHP safe
安装concrete5.4.2.1时出现You must chmod 755 concrete/libraries/3rdparty/htmldiff.py and disable PHP safe 如何解决？

[解决办法]
这个提示不是已经很清楚了嘛?
给这个文件相应的755权限.