Heroku python-3.6.1 runtime by default

Effective Tuesday, June 20th, 2017, new Python applications pushed to Heroku will use the python-3.6.1 runtime by default (instead of python-2.7.13).
Existing applications will not be affected by this change.
If you would like to specify Python 2.7, rather than using the new default, please refer to the Heroku Dev Center.
Many thanks,
The Heroku Python Team