Hello,

The attached patch adds the variable name to the `setopt` warning.

I write my Emacs config in an Org file, from which I make the Emacs Lisp 
file.  Currently, if `setopt` detects that the value I wish to make a 
variable hold does not conform to the variable's Custom.el type, then it 
reports the type and the problematic value, but not the variable itself, 
when I open Emacs.  This adds extra steps to editing the code in the Org 
file to fix the warning, especially when the value is created 
programmatically.  It would be faster to search for the variable name 
directly in the Org file and to then re-tangle the Org file.

Thank you.