Native Zuul v3 jobs (almost all of them)

It defines buildimages/CLI jobs, and reuses the global pylint job
and few jobs from sahara-tests (scenario, tempest), mimicking
the existing definitions of the legacy jobs.

Still missing: grenade (there is no common grenade job yet at this
point).

Change-Id: Ibb57e216410afeef4d55d8ba2576aaacfa2f8c1a

.zuul.yaml

@@ -0,0 +1,44 @@
+- project:
+    check:
+      jobs:
+        - openstack-tox-pylint:
+            voting: false
+        - sahara-tests-scenario
+        - sahara-tests-scenario-modwsgi:
+            voting: false
+        - sahara-tests-tempest
+    gate:
+      jobs:
+        - sahara-tests-scenario
+        - sahara-tests-tempest
+    experimental:
+      jobs:
+        - sahara-buildimages-ambari
+        - sahara-buildimages-cloudera
+        - sahara-buildimages-mapr
+        - sahara-tests-scenario-multinode-spark
+        - sahara-tests-scenario-py3
+
+- job:
+    name: sahara-buildimages-base
+    nodeset: centos-7
+    run: playbooks/buildimages/run.yaml
+    timeout: 7200
+
+- job:
+    name: sahara-buildimages-ambari
+    parent: sahara-buildimages-base
+    vars:
+      sahara_plugin: ambari
+
+- job:
+    name: sahara-buildimages-cloudera
+    parent: sahara-buildimages-base
+    vars:
+      sahara_plugin: cloudera
+
+- job:
+    name: sahara-buildimages-mapr
+    parent: sahara-buildimages-base
+    vars:
+      sahara_plugin: mapr

playbooks/buildimages/run.yaml

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+- hosts: all
+  roles:
+    - role: bindep
+      bindep_profile: test
+      bindep_dir: "{{ zuul.project.src_dir }}"
+    - build-sahara-images-cli

roles/build-sahara-images-cli/README.rst

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+Build Sahara Images with CLI
+
+**Role Variables**
+
+.. zuul:rolevar:: sahara_build_directory
+   :default: /var/tmp/sahara-image-build
+
+   The base directory used for the build process.
+
+.. zuul:rolevar:: sahara_plugin
+   :default: vanilla
+
+   The plugin whose images will be built.

roles/build-sahara-images-cli/defaults/main.yaml

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+---
+sahara_src_dir: "{{ ansible_user_dir }}/{{ zuul.projects['git.openstack.org/openstack/sahara'].src_dir }}"
+sahara_build_directory: /var/tmp/sahara-image-build
+sahara_plugin: vanilla

roles/build-sahara-images-cli/tasks/main.yaml

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+- name: Build all the images for the selected plugin
+  command: ./tools/gate/build-images "{{ sahara_plugin }}"
+  args:
+    chdir: "{{ sahara_src_dir }}"