Mark: Serhiy is asking that we not make the change to maintenance releases, 2.7 and 3.4, without further discussion and agreement.  He is correct to do so.  I reread PEP 434 and it specifically says  "The PEP would apply to ..., but not necessarily to possible major re-writes such as switching to themed widgets ... ."  'Not necessarily' means 'only permitted with further discussion.  Further discussion should continue on #24759 which is specifically about this issue.