Problem around custom-push-theme

[Stefan Monnier]

If a variable is set and we try to define a (not yet existing) face of the
same name with custom-set-face, it seems that custom-push-theme gets
confused and infers from boundp that the symbol is a valid face:

E.g. the following command:

   src/emacs -q --no-site-file --eval "(progn (setq ott1 'o) (custom-set-faces 
'(ott1 nil)))"

leads to an error whose backtrace looks like:

   Debugger entered--Lisp error: (error "Invalid face" ott1)
     internal-get-lisp-face-attribute(ott1 :family nil)
     face-attribute(ott1 :family nil)
     custom-face-attributes-get(ott1 nil)
     custom-push-theme(theme-face ott1 user set nil)
     custom-theme-set-faces(user ...)
     apply(custom-theme-set-faces user ...)
     custom-set-faces(...)


-- Stefan