This is done through a total rewrite of boto to support Python 2/3 [1]. And, as they say, "It's not production ready". So, It might be a little bit early to say that boto support Python 3 since every sub-module will need to be ported to be as usable as boto (to support each AWS service).

This is an outsider opinion on the project, if someone know more about it, don't hesitate to show me wrong.

[1]: see https://github.com/boto/boto3