That is not an uncommon and even not rare when an application which was supposed to be a prototype suddenly becomes a tool for everyday usage. Not a perfect thing here is that in a rush to make the program more or less user-friendly a developer has to hide internals by preserving error messages with internal details. Here I am going to share the pattern I mostly use in my “so-called-prototype” Python scripts; especially when they are translated to binaries using py2exe.
By default XFCE is shipped with a quite ascetic xscreensaver. Some people may find it not attractive. So I do also. For example, if you install an alternative screen locking application called i3lock there are about no chances that it will be used by XFCE. Even there are no other alternatives installed. Because XFCE knows nothing about it. But user definitely knows and wants to replace the default screensaver with a preferred one.