PEP 494: Python 3.6 is slated for release in late 2016
Travis-CI's 'latest' target switched to 3.6 alphas, and broke Pywikibot builds. We can expect many more breakages wrt 3.6 as the devs cut and hack.
Python 3.5 is not (yet?) listed as a target on http://docs.travis-ci.com/user/languages/python/ ; Reported Upstream as https://github.com/travis-ci/travis-ci/issues/4437