Fix markup glitch in unittest docs. Will backport.
diff --git a/Doc/lib/libunittest.tex b/Doc/lib/libunittest.tex
index 6c8769d..51b321e 100644
--- a/Doc/lib/libunittest.tex
+++ b/Doc/lib/libunittest.tex
@@ -226,7 +226,7 @@
identify the test case as a \dfn{failure}. Other exceptions that do
not arise from checks made through the \method{assert*()} and
\method{fail*()} methods are identified by the testing framework as
-dfn{errors}.
+\dfn{errors}.
The way to run a test case will be described later. For now, note
that to construct an instance of such a test case, we call its