showwarning() calls formatwarning(), not showwarning().

Bugfix candidate.

Doc/lib/libwarnings.tex

@@ -184,7 +184,7 @@ in which case \var{category} will be ignored.
 \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