Change \code to \verb, because TeX merges the two dashes into a

hyphen, resulting in the output '-list-classifiers', not the correct
'--list-classifiers'.  I've verified that the line is now correct
in the DVI, PDF, HTML, and ASCII versions.

Doc/whatsnew/whatsnew23.tex

@@ -757,7 +757,7 @@ core.setup(**kw)
 \end{verbatim}
 
 The full list of classifiers can be obtained by running 
-\code{python setup.py register --list-classifiers}.
+\verb|python setup.py register --list-classifiers|.
 
 \begin{seealso}