Patch #1015021: Stop claiming that coerce can return None.
Will backport to 2.3.
diff --git a/Doc/lib/libfuncs.tex b/Doc/lib/libfuncs.tex
index 1130eb1..d210510 100644
--- a/Doc/lib/libfuncs.tex
+++ b/Doc/lib/libfuncs.tex
@@ -1180,7 +1180,7 @@
\begin{funcdesc}{coerce}{x, y}
Return a tuple consisting of the two numeric arguments converted to
a common type, using the same rules as used by arithmetic
- operations.
+ operations. If coercion is not possible, raise \exception{TypeError}.
\end{funcdesc}
\begin{funcdesc}{intern}{string}