bug#16677: 24.3.50; Wrong type argument: char-or-string-p, 67108923

[Eli Zaretskii]

> From: Juanma Barranquero <lekktu@gmail.com>
> Date: Fri, 7 Feb 2014 04:55:04 +0100
> Cc: 16677@debbugs.gnu.org
> 
> +    (unless (characterp char)
> +      (user-error "%s is not a character"
> +                  (help-key-description (vector char) nil)))

"%s is not a valid character" is a better error message, IMO.