https://askubuntu.com/questions/635779/e45-readonly-option-is-set-add-to-override
It just means that I don't have the permission to save the file. So I need to add "sudo" in front of the command.
$ vi museum.stopabuse.me
//It could not save and print the error message.
$ sudo vi museum.stopabuse.me
//when I added sudo in front of the command and save, it worked