Lib/lib-tk/test/test_tkinter/test_loadtk in order to follow the behaviour of
test_ttkguionly.

(On windows, you still have to change one line to use pywin32
instead of the _subprocess helper module)

Issue 6288: update the contextlib.nested() docs to explain why it has been deprecated and should generally be avoided

Ensure that the snippet in doctest_aliases actually contains aliases.

(On Unix) Patch by STINNER Victor.