Add non-OpenStack python tarball creation job

OpenStack python tarball building is weird and not done in a manner
consistent with how other folks do it. Make a job that just runs python
setup.py sdist bdist_wheel.

Change-Id: I0df77cdd00b9820bad3b9cde75be9e150057a584

playbooks/python/sdist.yaml

@@ -0,0 +1,3 @@
+- hosts: all
+  roles:
+    - build-python-sdist

roles/build-python-sdist/defaults/main.yaml

@@ -0,0 +1 @@
+python_sdist_chdir: "src/{{ zuul.project.canonical_name }}"

roles/build-python-sdist/tasks/main.yaml

@@ -0,0 +1,4 @@
+- name: Build a tarball and wheel
+  command: python setup.py sdist bdist_wheel
+  args:
+    chdir: "{{ python_sdist_chdir }}"

zuul.yaml

@@ -117,6 +117,13 @@
     vars:
       tox_envlist: cover
 
+- job:
+    name: python-sdist
+    description: |
+      Build a source tarball and wheel for uploading
+    run: playbooks/python/sdist.yaml
+    post-run: playbooks/python/tarball-post
+
 - job:
     name: tox-tarball
     parent: tox