Fix a markup error:  do not omit a method's parameter list if it is
empty.
diff --git a/Doc/lib/liburllib2.tex b/Doc/lib/liburllib2.tex
index ddf89ee..0be3bbb 100644
--- a/Doc/lib/liburllib2.tex
+++ b/Doc/lib/liburllib2.tex
@@ -560,6 +560,6 @@
 
 \subsection{UnknownHandler Objects \label{unknown-handler-objects}}
 
-\begin{methoddesc}[UnknownHandler]{unknown_open}
+\begin{methoddesc}[UnknownHandler]{unknown_open}{}
 Raise a \exception{URLError} exception.
 \end{methoddesc}