The schedule for the deprecation of Python 2 support set by DM management is as follows:
- The 14.0 release that is just about to go out carries a deprecation notice linking to this post
- The next official release (15.0, ETA early 2018) will be the last release that will be supported under Python 2
- The next official release after that, version 16.0, will be Python 3 only
The adoption of Python 3 as the delivery standard is LSST-wide  and takes into consideration that Python 2 will be end-of-lifed by the start of LSST operations. Developers are keen to take advantages of powerful Python-3 only features, and consolidating on one major language version will allow SQuaRE to effectively double the number of nodes in the CI pool thus reducing developer wait times.
- All DM code under SQuaRE’s continuous integration is being tested and has worked under Python 3 (this has been the case for more than a year now).
- Any code written to back server-side services can be Python-3-only already 
- We believe all DM code in the Github LSST org is Python-3 compatible. Please let us know if this is not the case.
- If you have code that SQuaRE has no visibility into that is intended for LSST operations, you should be making arrangements with your T/CAM about porting it if you haven’t already. All DM Python code must work with Python 3 
If you are a science user and have personal code you wish to keep compatible with the LSST stack, you might find DM’s porting guide useful: SQR-014
 see Developer Guide