[ClusterLabs] Proposed change for 1.1.16: ending python 2.6 compatibility

[Ken Gaillot]

As you may be aware, python 3 is a significant, backward-compatible
restructuring of the python language. Most development of the python 2
series has ended, and support for python 2 will completely end in 2020.

Pacemaker currently uses python only in its test suites. At some point,
we may convert a few existing Pacemaker-provided resource agents and
fence agents to python as well.

Currently, Pacemaker's python code is compatible with python 2.6 and
2.7. We definitely need to start moving toward python 3 compatibility.
It is possible to support both 2.7 and 3 with the same code, but we need
to lose compatibility with 2.6. (Maintaining a separate branch of code
for 2.6 would not be worth the effort.)

So, I propose that Pacemaker stop supporting python 2.6 as of the next
version (1.1.16, expected sometime in the fall or winter). Not all our
python code is likely to be python3-compatible by that time, but we can
start moving in that direction.

If anyone has any reasons to do this differently, let me know. As this
only affects the test suites currently, and most Linux distributions
have stopped supporting python 2.6 already, I expect more "what took you
so long" responses than "slow down" ;-)
-- 
Ken Gaillot <kgaillot at redhat.com>