While not great for migration uWSGI also has chain reloading [1] which will do the same thing as killing each worker. I use Tornado at work for some applications so I had to come up with something for Gunicorn as uWSGI + Tornado doesn't really fit together.

  [1] http://uwsgi-docs.readthedocs.org/en/latest/Changelog-1.9.html#chain-reloading