Open Stack

Hello Everyone,

We are in Ussuri development cycle which is planned to drop the py2.7 support[1].

I was holding and planning to support the py2.7 in Tempest due to its branchless model[2]. My main point
to keep py2 support is if any users running the Tempest on py27 env cloud and not in virtual env then they
can keep running in the same way.  But this might be just me overthinking on this usage. 

What happens if we drop py2.7 from Tempest:
* Users with the above case have the way to install the latest Tempest on virtual env of py3. or use 
   the Tempest tag if they do not need latest Tempest.
* No change in users using Tempest on py3 or in py3 virtual env.
* Upstream testing of master or stable branch is no issue as we install the Tempest in virtual env.
   Tempest in py3 venv can always test the py2.7 jobs.
* other than that no change in Tempest usage or at least it would not break anything. 

Why we cannot keep the support:
There is no big cost of supporting the py2.7 in Tempest itself but that require Temepst dependency
(OpenStack lib like Oslo and non-openstack maintained lib [3]) to keep supporting the py2.7 which is not
feasible.

Other solution:
One way is to cut the Tempest stable branch and keep the py2.7 support there with eligible backport from Tempest
master which is py3 only. But I would say, QA team has no bandwidth to do so. if anyone wants to maintain that then
we can discuss this option in more detail. 

I have given a second thought on this and now ok to drop the py2.7 from Tempest by considering all the above points. 
Please reply if any disagreement on this or add if anything I missed to consider. 

NOTE: Tempest includes its plugins also.

[1] http://lists.openstack.org/pipermail/openstack-discuss/2019-October/010142.html
[2] https://review.opendev.org/#/c/681203/
[3] https://opendev.org/openstack/tempest/src/commit/7fdd39c6dbde37bccd419c4037e1e352a5189c5a/requirements.txt


-gmann