Switch Refstack image over to python3.9

Refstack is running python3.9 jobs now and they appear to be passing.
Update our image to python3.9 so that we are consistently using
python3.9 in as many locations as possible. Maybe one day we can drop
the 3.7 and 3.8 image builds too.

Change-Id: Iadb84f8f3756fe717ab6bcda0303bc23ff69ad6d

docker/refstack/Dockerfile

@@ -16,7 +16,7 @@
 # upload trigger - Mon 26 Oct 2021 06:00 PM UTC
 # refstack commit - bb0e985734690394e227d16af893b8e4ac8d3724
 
-FROM opendevorg/python-builder:3.8-bullseye as builder
+FROM opendevorg/python-builder:3.9-bullseye as builder
 
 RUN apt-get update \
   && apt-get -y install git apt-utils python3-dev dh-python libc-dev-bin \
@@ -43,7 +43,7 @@ RUN python -m venv /tmp/venv \
   && /tmp/venv/bin/python /tmp/src/tools/convert-docs.py -o /tmp/src/refstack-ui/app/components/about/templates /tmp/src/doc/source/*.rst \
   && rm -rf /tmp/venv
 
-FROM opendevorg/python-base:3.8-bullseye as refstack
+FROM opendevorg/python-base:3.9-bullseye as refstack
 
 COPY --from=builder /output/ /output
 COPY --from=builder /tmp/src/refstack-ui/app/ /refstack-ui/app
@@ -55,4 +55,4 @@ RUN /output/install-from-bindep \
   && rm -rf /output
 
 ENTRYPOINT ["/usr/bin/entrypoint"]
-CMD ["pecan", "serve", "/usr/local/lib/python3.8/site-packages/refstack/api/config.py"]
+CMD ["pecan", "serve", "/usr/local/lib/python3.9/site-packages/refstack/api/config.py"]

zuul.d/docker-images/refstack.yaml

@@ -4,8 +4,8 @@
     description: Build a refstack image.
     parent: system-config-build-image
     requires: &refstack_requires
-      - python-base-3.8-bullseye-container-image
-      - python-builder-3.8-bullseye-container-image
+      - python-base-3.9-bullseye-container-image
+      - python-builder-3.9-bullseye-container-image
     provides: refstack-container-image
     vars: &refstack_vars
       docker_images: