\begin{thebibliography}{}
\expandafter\ifx\csname fonteauteurs\endcsname\relax
\def\fonteauteurs{\scshape}\fi
\expandafter\ifx\csname url\endcsname\relax
\def\url#1{{\tt #1}}%
\message{You should include the url package}\fi
\end{thebibliography}