Prepare to drop Python 2 support

Pin func test requirements to stable/train; the last stable release
with Python 2 support.  Switch to the python-jobs-no-constraints
template to avoid using master constraints file.

Only build focal on bionic, other debootstraps are too old.

Remove pip-and-virtualenv testing as we are moving to plain images.

The tripleo-buildimage-jobs are unstable; see linked bug.

Add a note that this is the last Python 2 release.

Change-Id: Ibde7a564dd41cc2d6e80e2dffe5a95a57bbf8ada

.zuul.d/jobs.yaml

@@ -7,7 +7,8 @@
     timeout: 5400
     required-projects:
       - openstack/diskimage-builder
-      - openstack/requirements
+      - name: openstack/requirements
+        override-checkout: stable/train
     irrelevant-files:
       - ^.*\.rst$
       - ^doc/.*$
@@ -23,10 +24,8 @@
         - apt-sources/test-sources
         - centos-minimal/7-build-succeeds
         - centos-minimal/8-build-succeeds
-        - pip-and-virtualenv/source-install-ubuntu
         - ubuntu-minimal/xenial-build-succeeds
         - ubuntu-minimal/bionic-build-succeeds
-        - ubuntu-minimal/focal-build-succeeds
 
 - job:
     name: dib-functests-image
@@ -95,6 +94,7 @@
       # These can only build on bionic
       dib_functests_extra:
         - fedora-minimal/build-succeeds
+        - ubuntu-minimal/focal-build-succeeds
 
 - job:
     name: dib-functests-bionic-python3-image
@@ -130,10 +130,6 @@
       Run the default tests on a Xenial build host with Python 3
     parent: dib-functests-default
     nodeset: ubuntu-xenial
-    vars:
-      dib_functests_extra:
-        # Only builds on xenial; should work on focal in future
-        - pip-and-virtualenv/source-install-opensuse
 
 - job:
     name: dib-functests-xenial-python3-image

.zuul.d/project.yaml

@@ -3,10 +3,12 @@
       - openstack-cover-jobs
       - check-requirements
       - openstack-lower-constraints-jobs
-      - openstack-python-jobs
+      - openstack-python-jobs-no-constraints
       - openstack-python35-jobs
       - release-notes-jobs
-      - tripleo-buildimage-jobs
+      # NOTE(ianw): 2020-05-29 jobs are unstable; see
+      # https://bugs.launchpad.net/tripleo/+bug/1879766
+      # - tripleo-buildimage-jobs
     check:
       jobs:
         - openstack-tox-pylint

releasenotes/notes/create-945440b17d500bf5.yaml

@@ -0,0 +1,4 @@
+---
+critical:
+  - |
+    This is the last release of diskimage-builder to support Python 2

tox.ini

@@ -7,7 +7,7 @@ skipsdist = True
 usedevelop = True
 install_command = pip install {opts} {packages}
 deps=
-      -c{env:UPPER_CONSTRAINTS_FILE:https://opendev.org/openstack/requirements/raw/branch/master/upper-constraints.txt}
+      -c{env:UPPER_CONSTRAINTS_FILE:https://opendev.org/openstack/requirements/raw/branch/stable/train/upper-constraints.txt}
       -r{toxinidir}/requirements.txt
       -r{toxinidir}/test-requirements.txt
 commands=