CentOS 8 minimal testing and support

This adds CentOS 8 into functional and boot tests.

This completes centos-minimal support, documentation is updated and a
release note is added.

Change-Id: I435c2967b4f49faeb6d6edf189907b9f96e80357

.zuul.d/jobs.yaml

@@ -21,7 +21,8 @@
     vars:
       dib_functests:
         - apt-sources/test-sources
-        - centos-minimal/build-succeeds
+        - centos-minimal/7-build-succeeds
+        - centos-minimal/8-build-succeeds
         - fedora-minimal/build-succeeds
         - ironic-agent/build-succeeds-fedora
         - pip-and-virtualenv/source-install-fedora
@@ -224,6 +225,20 @@
         release: '7'
         mirror: "http://{{ zuul_site_mirror_fqdn }}/centos"
 
+- job:
+    name: dib-nodepool-functional-openstack-centos-8-src
+    description: |
+      Test building and booting a Centos 8 image with Nodepool and OpenStack
+    parent: dib-nodepool-functional-src-base
+    vars:
+      nodepool_extra_packages:
+        - rpm
+        - yum-utils
+      nodepool_diskimage:
+        base_element: centos-minimal
+        release: '8'
+        mirror: "http://{{ zuul_site_mirror_fqdn }}/centos"
+
 - job:
     name: dib-nodepool-functional-openstack-fedora-29-src
     description: |

.zuul.d/project.yaml

@@ -11,6 +11,7 @@
       jobs:
         - openstack-tox-pylint
         - dib-nodepool-functional-openstack-centos-7-src
+        - dib-nodepool-functional-openstack-centos-8-src
         - dib-nodepool-functional-openstack-fedora-29-src
         - dib-nodepool-functional-openstack-fedora-30-src
         - dib-nodepool-functional-openstack-opensuse-15-src
@@ -36,6 +37,7 @@
       jobs:
         - openstack-tox-pylint
         - dib-nodepool-functional-openstack-centos-7-src
+        - dib-nodepool-functional-openstack-centos-8-src
         - dib-nodepool-functional-openstack-fedora-29-src
         - dib-nodepool-functional-openstack-fedora-30-src
         - dib-nodepool-functional-openstack-opensuse-15-src

diskimage_builder/elements/centos-minimal/README.rst

@@ -6,6 +6,9 @@ Create a minimal image based on CentOS
 Use of this element will require 'yum' and 'yum-utils' to be installed on
 Ubuntu and Debian. Nothing additional is needed on Fedora or CentOS.
 
+By default this builds CentOS 7 images.  Set ``DIB_RELEASE`` to ``7``
+or ``8`` to explicitly select the release.
+
 For CentOS 7, by default, ``DIB_YUM_MINIMAL_CREATE_INTERFACES`` is set
 to enable the creation of
 ``/etc/sysconfig/network-scripts/ifcfg-eth[0|1]`` scripts to enable

diskimage_builder/elements/centos-minimal/test-elements/8-build-succeeds/README.rst

@@ -0,0 +1 @@
+Verify we can build a centos-minimal image.

diskimage_builder/elements/centos-minimal/test-elements/8-build-succeeds/element-deps

@@ -0,0 +1 @@
+openstack-ci-mirrors

diskimage_builder/elements/centos-minimal/test-elements/8-build-succeeds/environment.d/09-set-distro.bash

@@ -0,0 +1 @@
+export DIB_RELEASE='8'

releasenotes/notes/centos-minimal-8-aca6314862741177.yaml

@@ -0,0 +1,5 @@
+---
+features:
+  - |
+    The ``centos-minimal`` supports CentOS 8 builds when run with
+    ``DIB_RELEASE=8``