Bug #1337990: clarified that `doctest` does not support examples
requiring both expected output and an exception.
I'll backport to 2.4 next.
diff --git a/Doc/lib/libdoctest.tex b/Doc/lib/libdoctest.tex
index 0e3a017..7c4cb41 100644
--- a/Doc/lib/libdoctest.tex
+++ b/Doc/lib/libdoctest.tex
@@ -407,10 +407,13 @@
\subsubsection{What About Exceptions?\label{doctest-exceptions}}
No problem, provided that the traceback is the only output produced by
-the example: just paste in the traceback. Since tracebacks contain
-details that are likely to change rapidly (for example, exact file paths
-and line numbers), this is one case where doctest works hard to be
-flexible in what it accepts.
+the example: just paste in the traceback.\footnote{Examples containing
+ both expected output and an exception are not supported. Trying
+ to guess where one ends and the other begins is too error-prone,
+ and that also makes for a confusing test.}
+Since tracebacks contain details that are likely to change rapidly (for
+example, exact file paths and line numbers), this is one case where doctest
+works hard to be flexible in what it accepts.
Simple example: