Change {\em ...} to \emph{...} for consistency with the rest of the Python
documentation.
diff --git a/Doc/lib/libdoctest.tex b/Doc/lib/libdoctest.tex
index 8adbc9d..6d19259 100644
--- a/Doc/lib/libdoctest.tex
+++ b/Doc/lib/libdoctest.tex
@@ -207,7 +207,7 @@
\subsection{What's the Execution Context?}
By default, each time testmod finds a docstring to test, it uses a
-{\em copy} of \module{M}'s globals, so that running tests on a module
+\emph{copy} of \module{M}'s globals, so that running tests on a module
doesn't change the module's real globals, and so that one test in
\module{M} can't leave behind crumbs that accidentally allow another test
to work. This means examples can freely use any names defined at top-level