SF patch #1056967, changes the semantics of Template.safe_substitute() to not
raise a ValueError for dangling delimiters (the delimiter itself is returned).
diff --git a/Doc/lib/libstring.tex b/Doc/lib/libstring.tex
index c9d27b5..1828b2e 100644
--- a/Doc/lib/libstring.tex
+++ b/Doc/lib/libstring.tex
@@ -131,8 +131,16 @@
Like \method{substitute()}, except that if placeholders are missing from
\var{mapping} and \var{kws}, instead of raising a \exception{KeyError}
exception, the original placeholder will appear in the resulting string
-intact. Note that other exceptions may still be raised, including
-\exception{ValueError} as described above.
+intact. Also, unlike with \method{substitute()}, any other appearances of the
+\samp{\$} will simply return \samp{\$} instead of raising
+\exception{ValueError}.
+
+While other exceptions may still occur, this method is called ``safe'' because
+substitutions always tries to return a usable string instead of raising an
+exception. In another sense, \method{safe_substitute()} may be anything other
+than safe, since it will silently ignore malformed templates containing
+dangling delimiters, unmatched braces, or placeholders that are not valid
+Python identifiers.
\end{methoddesc}
\class{Template} instances also provide one public data attribute: