showwarning() calls formatwarning(), not showwarning().
Bugfix candidate.
diff --git a/Doc/lib/libwarnings.tex b/Doc/lib/libwarnings.tex
index e8c92e4..d829b10 100644
--- a/Doc/lib/libwarnings.tex
+++ b/Doc/lib/libwarnings.tex
@@ -184,7 +184,7 @@
\begin{funcdesc}{showwarning}{message, category, filename,
lineno\optional{, file}}
Write a warning to a file. The default implementation calls
-\code{showwarning(\var{message}, \var{category}, \var{filename},
+\code{formatwarning(\var{message}, \var{category}, \var{filename},
\var{lineno})} and writes the resulting string to \var{file}, which
defaults to \code{sys.stderr}. You may replace this function with an
alternative implementation by assigning to