Emacs messages

[Christopher Dimech]

Dear Compeers, 

I have an extensive number of .el files I use to customise emacs.
A few moments ago I made changes to the code and kept one variable
unmodified as `sel' rather than using `selection'.

Emacs complained with

  cond: Symbol’s value as variable is void: sel

It would be instructive for users if emacs include additional information,
like the file name and line number associated with the detected `cond' problem.

Regards
Christopher