watcher 0.28.0 release

meta:version: 0.28.0
meta:series: newton
meta:release-type: release
meta:announce: openstack-announce@lists.openstack.org
meta:pypi: no
meta:first: no
meta:release:Author: Antoine Cabot <antoine.cabot@b-com.com>
meta:release:Commit: Antoine Cabot <antoine.cabot@b-com.com>
meta:release:Change-Id: I3aa1670d6b3648149bce6000e9e0ffbe850d1b50
meta:release:Code-Review+2: Doug Hellmann <doug@doughellmann.com>
meta:release:Workflow+1: Doug Hellmann <doug@doughellmann.com>

0.26.0 tag