Python 3.4 was released over a month ago. According to this announcement, Travis CI will finally support Python 3.4 in only a few hours. This has been long awaited by the community, given the many "+1" postings in Travis CI issue 1989 and the countless "Add 3.4 to .travis.yml"-style commit messages referencing this issue.

Many believe that Python 3.4 will be the breakthrough for Python 3 and we can expect it to become quite popular. Although Python 2.7 security and bug fixes have recently been “guaranteed” for up to 2020 by Guido, I got the impression that the dominance of Python 2.7 finally decreases — slowly, but steadily. For developers in the open source community this means that Python 3.4 compatibility is an important target to aim for now (you might even want to ignore all releases up to 3.3).

By the way, Ubuntu has made Python 3.4 the default Python 3 in their recently released 14.04 LTS (which will be supported for 5 years). They even considered to ship it as the default Python which they did not do in the end — their recommendation, however, is

“to best support future versions of Ubuntu you should consider porting your code to Python 3”

So, go ahead, use the great Travis CI and make your code run on both, Python 2.7 and Python 3.4!