It's time to drop Python 2.6 support in Robot Framework 3.1.

The main motivation:

• Python 2.6 hasn't been officially supported, even with security updates, since October 2013.
• Supporting Python 2.6 requires some time. That time is better spent fixing bugs and developing new features.
• We get to use set literals, dict comprehensions, and other such syntax and modules not supported by Python 2.6.
• All test libraries and other code running on Python 2.6 ought to run unchanged on Python 2.7. Upgrading is thus only matter of upgrading the underlying Python version. If that is impossible, it is unlikely these users can upgrade to newer RF releases either.
• Users of older RedHat based Linux distributions that only contain Python 2.6 by default can easily install Python 2.7 from the official Software Collections repository.

For some more reasoning see http://www.snarky.ca/stop-using-python-2-6. Notice that we do not plan to drop Python 2.7 support in the foreseeable future.