Fix amphora image build

DIB dropped Python 2 support in its version 3.0.0 major release and as
so we had to pin it to 2.30.0 in stable/stein and stable/train branches.
However, upstream get-pip.sh recently introduced a regression where it
does not work well with Python <-3.5. Sadly, DIB 2.30.0 points to master
get-pip.sh [1] and DIB is branchless so the fix cannot be backported and
we are in a deadlock scenario where Python <=3.5 amphora images can't be
built.

To work-around this issue on stable/train, we have to make a compromise:
either build amphora images using master DIB and Python 3 only or be
stuck (unless someone else can come up with another approach, all ears).
Ussuri and newer releases are not impacted by this issue as they are
Python >=3.6 only releases.

The same issue also applies to Stein and that has an impact on the
octavia-grenade CI job in stable/train. Since Stein Octavia is EOL [2],
we no longer have to test upgrades.

[1] https://review.opendev.org/c/openstack/diskimage-builder/+/772254
[2] https://review.opendev.org/c/openstack/releases/+/772847

Change-Id: I13da9a49ace803e957dc52e4882b78141bc7bef3

devstack/plugin.sh

@@ -98,7 +98,20 @@ function build_octavia_worker_image {
         fi
         sudo mkdir -m755 ${dib_logs}
         sudo chown $STACK_USER ${dib_logs}
-        $OCTAVIA_DIR/diskimage-create/diskimage-create.sh -l ${dib_logs}/$(basename $OCTAVIA_AMP_IMAGE_FILE).log $octavia_dib_tracing_arg -o $OCTAVIA_AMP_IMAGE_FILE ${PARAM_OCTAVIA_AMP_BASE_OS:-} ${PARAM_OCTAVIA_AMP_DISTRIBUTION_RELEASE_ID:-} ${PARAM_OCTAVIA_AMP_IMAGE_SIZE:-}
+        # Build amphora image with master DIB in a Python 3 virtual environment
+        (
+            DIB_VENV_DIR=$(mktemp -d)
+            DIB_GIT_DIR=/tmp/dib-octavia
+            python3 -m venv $DIB_VENV_DIR
+            export USE_PYTHON3=True
+            export PATH=$DIB_VENV_DIR/bin:$PATH
+            if ! [ -d $DIB_GIT_DIR ]; then
+                git clone ${GITREPO["diskimage-builder"]} $DIB_GIT_DIR
+            fi
+            (cd $REQUIREMENTS_DIR && git show origin/master:upper-constraints.txt) | sed '/diskimage-builder/d' > $DIB_VENV_DIR/u-c.txt
+            pip install -c $DIB_VENV_DIR/u-c.txt $DIB_GIT_DIR
+            $OCTAVIA_DIR/diskimage-create/diskimage-create.sh -l ${dib_logs}/$(basename $OCTAVIA_AMP_IMAGE_FILE).log $octavia_dib_tracing_arg -o $OCTAVIA_AMP_IMAGE_FILE ${PARAM_OCTAVIA_AMP_BASE_OS:-} ${PARAM_OCTAVIA_AMP_DISTRIBUTION_RELEASE_ID:-} ${PARAM_OCTAVIA_AMP_IMAGE_SIZE:-}
+        )
     fi
     upload_image file://${OCTAVIA_AMP_IMAGE_FILE} $TOKEN
 

zuul.d/jobs.yaml

@@ -69,19 +69,6 @@
         amphora_image_size: 3
         amphora_os_release: 28
 
-- job:
-    name: octavia-grenade
-    parent: octavia-legacy-dsvm-base
-    run: playbooks/legacy/grenade-devstack-octavia/run.yaml
-    post-run: playbooks/legacy/grenade-devstack-octavia/post.yaml
-    required-projects:
-      - openstack/grenade
-      - openstack/devstack-gate
-      - openstack/octavia
-      - openstack/octavia-lib
-      - openstack/octavia-tempest-plugin
-      - openstack/python-octaviaclient
-
 - job:
     name: octavia-v2-dsvm-scenario-amphora-v2
     parent: octavia-v2-dsvm-scenario

zuul.d/projects.yaml

@@ -38,17 +38,6 @@
             voting: false
         - octavia-v2-dsvm-py2-scenario-two-node:
             voting: false
-        - octavia-grenade:
-            irrelevant-files:
-              - ^.*\.rst$
-              - ^api-ref/.*$
-              - ^doc/.*$
-              - ^octavia/tests/unit/.*$
-              - ^releasenotes/.*$
-              - ^setup.cfg$
-              - ^tools/.*$
-              - ^(test-|)requirements.txt$
-              - ^tox.ini$
         - octavia-v2-dsvm-tls-barbican:
             irrelevant-files:
               - ^.*\.rst$
@@ -92,17 +81,6 @@
         - octavia-v2-dsvm-noop-api
         - octavia-v2-dsvm-noop-py2-api
         - octavia-v2-dsvm-scenario
-        - octavia-grenade:
-            irrelevant-files:
-              - ^.*\.rst$
-              - ^api-ref/.*$
-              - ^doc/.*$
-              - ^octavia/tests/unit/.*$
-              - ^releasenotes/.*$
-              - ^setup.cfg$
-              - ^tools/.*$
-              - ^(test-|)requirements.txt$
-              - ^tox.ini$
     periodic:
       jobs:
         - publish-openstack-octavia-amphora-image-xenial: