Add test.test_support.guard_warnings_filter . This function returns a context
manager that protects warnings.filter from being modified once the context is
exited.
diff --git a/Doc/lib/libtest.tex b/Doc/lib/libtest.tex
index 54a24b1..d13bfff 100644
--- a/Doc/lib/libtest.tex
+++ b/Doc/lib/libtest.tex
@@ -263,6 +263,10 @@
This does not equal a failure since it could be the path to the file.
\end{funcdesc}
+\begin{funcdesc}{guard_warnings_filter}{}
+Returns a context manager that guards the \module{warnings} module's
+filter settings.
+
\begin{funcdesc}{run_unittest}{*classes}
Execute \class{unittest.TestCase} subclasses passed to the function.
The function scans the classes for methods starting with the prefix