Unicode method on model should return unicode

The example of a __unicode__ model method should return a unicode value
instead of a string.
Fixed #22384 -- Deprecated reversing URLs by dotted path.
Merge pull request #2756 from tubaman/return_unicode

Unicode method on model should return unicode
Removed erroneous trailing comma in OLMapWidget.js.
Updated current state of MySQL Connector/Python.
Added a patch review checklist.
Fixed #22681 -- Made TarArchive recognize leading directories properly.