oslo.cache 2.8.0 release

meta:version: 2.8.0
meta:diff-start: -
meta:series: xena
meta:release-type: release
meta:pypi: yes
meta:first: yes
meta:release:Author: Hervé Beraud <hberaud@redhat.com>
meta:release:Commit: Hervé Beraud <hberaud@redhat.com>
meta:release:Change-Id: I709018dc678544915458aa8cbad8582956d32958
meta:release:Code-Review+2: Thierry Carrez <thierry@openstack.org>
meta:release:Code-Review+2: Elod Illes <elod.illes@est.tech>
meta:release:Workflow+1: Elod Illes <elod.illes@est.tech>