Update the docker images to python 3.10

We do this to take advantage of python 3.10's speed improvements as
illustrated by Zuul proper. But also OpenDev would like to drop python
3.8 image builds to make room for python 3.11.

We add python3.10 unittesting to prevent regressing the docker images on
that version of python.

Change-Id: Ib2e39e0c5d09b4fdce40faa072fe51b55c8d7407

.zuul.yaml

@@ -23,10 +23,10 @@
     run: playbooks/functional-test/run.yaml
     post-run: playbooks/functional-test/post.yaml
     requires:
-      - python-builder-3.8-bullseye-container-image
-      - python-base-3.8-bullseye-container-image
+      - python-builder-3.10-bullseye-container-image
+      - python-base-3.10-bullseye-container-image
     provides: zuul-registry-container-image
-    nodeset: ubuntu-focal
+    nodeset: ubuntu-jammy
     vars: &image_vars
       docker_images:
         - context: .
@@ -44,14 +44,14 @@
     allowed-projects: zuul/zuul-registry
     run: playbooks/functional-test/run.yaml
     post-run: playbooks/functional-test/post.yaml
-    nodeset: ubuntu-focal
+    nodeset: ubuntu-jammy
     secrets:
       name: docker_credentials
       secret: zuul-registry-dockerhub
       pass-to-parent: true
     requires:
-      - python-builder-3.8-bullseye-container-image
-      - python-base-3.8-bullseye-container-image
+      - python-builder-3.10-bullseye-container-image
+      - python-base-3.10-bullseye-container-image
     provides: zuul-registry-container-image
     vars: *image_vars
 
@@ -76,12 +76,16 @@
         - zuul-registry-build-image
         - tox-pep8
         - tox-py38
+        - tox-py310:
+            nodeset: ubuntu-jammy
         - build-python-release
     gate:
       jobs:
         - zuul-registry-upload-image
         - tox-pep8
         - tox-py38
+        - tox-py310:
+            nodeset: ubuntu-jammy
         - build-python-release
     promote:
       jobs:

Dockerfile

@@ -13,12 +13,12 @@
 # You should have received a copy of the GNU General Public License
 # along with this software.  If not, see <http://www.gnu.org/licenses/>.
 
-FROM opendevorg/python-builder:3.8-bullseye as builder
+FROM opendevorg/python-builder:3.10-bullseye as builder
 
 COPY . /tmp/src
 RUN assemble
 
-FROM opendevorg/python-base:3.8-bullseye as zuul-registry
+FROM opendevorg/python-base:3.10-bullseye as zuul-registry
 
 COPY --from=builder /output/ /output
 RUN /output/install-from-bindep

zuul_registry/main.py

@@ -525,8 +525,8 @@ class RegistryServer:
 
     @staticmethod
     def load_config(path: str, env: typing.Dict[str, str]) -> typing.Any:
-        """Replace path content value of the form %(ZUUL_ENV_NAME) with environment,
-           Then return the yaml load result"""
+        """Replace path content value of the form %(ZUUL_ENV_NAME) with
+           environment, then return the yaml load result"""
         with open(path) as f:
             return yaml.safe_load(functools.reduce(
                 lambda config, env_item: config.replace(