Return face attribute KEYWORD of face SYMBOL.
If SYMBOL does not name a valid Lisp face or KEYWORD isn't a valid
face attribute name, signal an error.
If the optional argument FRAME is given, report on face SYMBOL in that
frame. If FRAME is t, report on the defaults for face SYMBOL (for new
frames). If FRAME is omitted or nil, use the selected frame.
(fn SYMBOL KEYWORD &optional FRAME)