slime-fancy interferes with customization of slime-completion-at-point-functions

[abrace]

The slime-fancy contrib, which is loaded by default, adds slime-c-p-c-completion-at-point to slime-completion-at-point-functions. If you view the Slime Completion At Point Functions setting in an Emacs customization buffer, Emacs reports that the setting has been changed outside Customize. If you do Erase Customization to return the setting to its default, there is no option to save the setting, and slime-c-p-c-completion-at-point will be back in slime-completion-at-point-functions in your next Emacs session.