drop python 2.7 support

[Ian Goodfellow]

Should we drop python 2.7 support and add CleverHans to the list of projects pledging to drop support?

https://python3statement.org/

If nothing else, this would make our Travis builds schedule 2X fewer jobs.

Concretely, I think this would involve dropping the python 2.7 jobs from .travis.yml and adding a statement to the readme saying that Python 2.7 will probably work but isn't officially tested anymore, and that we won't fix Python 2.7 bugs after 2019-07-04 (or 6 months from whatever date we choose to drop support).

[Nicholas Carlini]

Yes. Python3 is is 10 years old now. The world should move on.

Besides, Python2.7 will officially EOL in 2020.


Nicholas

> --
> You received this message because you are subscribed to the Google Groups "cleverhans dev" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to cleverhans-de...@googlegroups.com.
> To post to this group, send email to cleverh...@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/cleverhans-dev/CAG5SLK9Ofd_d%2Bv899UpRkJLUix3XJBrf3UwPkveNmfoEhUcLew%40mail.gmail.com.
> For more options, visit https://groups.google.com/d/optout.