Edit: It has now been released, see the reply below!
We are aiming for the first nightly release of Mantid that uses Python 3 to be the middle of next week (21st-22nd Jan 2020)!
This will allow you to properly test your converted Python scripts before our first full release with Python 3. Our second Python Migration Drop-in session is on Wednesday 22nd Jan so please come along to that if you have any questions.
As a reminder, we have migrated the Mantid Script Repository to be compatible with Python 3. The responsibility still lies with you to check your scripts run as intended as this isn’t something we can feasibly test ourselves.