* Recent versions of etcd no longer support the /v3alpha/ endpoint
* It's probably better to skip directly to the /v3/ endpoint
as a default.
* Note that this probably means a new minor version of tooz, while
the behaviour can be worked around in config, this is enough to
break existing systems on upgrade.
* Updated the test to test backwards compatibility.
* Updated the tests to use etcd 3.3.27, unfortunately we need
a newer version of pifpaf that supports 3.4 before the default
api can be used.
* The etcd backend tests have been removed: the deprecated backend
uses the v2 api which is no longer provided - a future commit
should remove the deprecated backend. The etcd3gw backend is the
replacement.
This fix is required in pifpaf, but it's not in any release:
7496e5e1c3
Depends-On: https://review.opendev.org/c/openstack/devstack/+/891353
Change-Id: Ibb5e587f6b1348794b1bf4d6405bc4a32a653c2c
Let's move on to newer releases of etcd. Especially since
3.1.x introduced some backwards incompatible changes
https://github.com/coreos/etcd/releases
Change-Id: I3887dbb745fb6de844c4b60d43b6543f441f239b