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Here's the notes from the actual release:
2015-11-17 - Django 1.8 Release/wiki/spaces/RELEASES/pages/46794141
Here's the retro notes:
Django 1.9 Upgrade Hackathon Project
As of June 2016, Django 1.9 is out and on version 1.9.7. It is not a long-term-support (LTS) release and we haven't made the decision to upgrade edx-platform's Django to it yet. However, it must happen eventually.
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