Update container image to bullseye and python3.9

We're trying to drop out the old images based on buster and 3.7 which
storyboard has based its images on. Update storyboard to bullseye and
python3.9 now that they have both been out for a while.

Depends-On: https://review.opendev.org/c/opendev/storyboard/+/838409
Change-Id: Ibf5f3eb63e22eb5b37cdfa74fe3bb6ce1f31bb62

.zuul.yaml

@@ -28,8 +28,8 @@
     dependencies: opendev-buildset-registry
     description: Build OpenDev Docker images for storyboard
     requires:
-      - python-base-container-image
-      - python-builder-container-image
+      - python-base-3.9-bullseye-container-image
+      - python-builder-3.9-bullseye-container-image
     provides: storyboard-container-image
     vars: &storyboard_opendev_image_vars
       zuul_work_dir: src/opendev.org/opendev/storyboard
@@ -61,8 +61,8 @@
     parent: opendev-upload-docker-image
     description: Build OpenDev storyboard Docker images and upload to Docker Hub.
     requires:
-      - python-base-container-image
-      - python-builder-container-image
+      - python-base-3.9-bullseye-container-image
+      - python-builder-3.9-bullseye-container-image
     provides: storyboard-container-image
     vars: *storyboard_opendev_image_vars
     secrets:

Dockerfile

@@ -13,12 +13,12 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-FROM opendevorg/python-builder as builder
+FROM opendevorg/python-builder:3.9-bullseye as builder
 
 COPY . /tmp/src
 RUN assemble
 
-FROM opendevorg/python-base as storyboard
+FROM opendevorg/python-base:3.9-bullseye as storyboard
 
 COPY --from=builder /output/ /output
 RUN /output/install-from-bindep