issue27202 - Fix the mistake in changesets 70af472451cb (3.5) and 2bb806539ca6 (3.6)

exclude_patterns in Sphinx conf.py will exclude the .rsts from the build. It
was incorrect exclude 2.x rsts in that.  This fix contributed again Jelle
Zijlstra, excludes doctests in whatsnew/2.7.rst from being exercised by using
doctests skip option.