Pin publish test to 3.12 (#8951)

The bump to 3.13 broke the test

.github/workflows/ci.yml

@@ -1139,6 +1139,7 @@ jobs:
     env:
       # No dbus in GitHub Actions
       PYTHON_KEYRING_BACKEND: keyrings.alt.file.PlaintextKeyring
+      PYTHON_VERSION: 3.12
     permissions:
       # For trusted publishing
       id-token: write
@@ -1149,7 +1150,7 @@ jobs:
 
       - uses: actions/setup-python@v5
         with:
-          python-version: "3.12"
+          python-version: "${{ env.PYTHON_VERSION }}"
 
       - name: "Download binary"
         uses: actions/download-artifact@v4
@@ -1169,7 +1170,7 @@ jobs:
 
       - name: "Publish test packages"
         # `-p 3.12` prefers the python we just installed over the one locked in `.python_version`.
-        run: ./uv run -p 3.12 scripts/publish/test_publish.py --uv ./uv all
+        run: ./uv run -p ${{ env.PYTHON_VERSION }} scripts/publish/test_publish.py --uv ./uv all
         env:
           RUST_LOG: uv=debug,uv_publish=trace
           UV_TEST_PUBLISH_TOKEN: ${{ secrets.UV_TEST_PUBLISH_TOKEN }}
@@ -1177,6 +1178,7 @@ jobs:
           UV_TEST_PUBLISH_GITLAB_PAT: ${{ secrets.UV_TEST_PUBLISH_GITLAB_PAT }}
           UV_TEST_PUBLISH_CODEBERG_TOKEN: ${{ secrets.UV_TEST_PUBLISH_CODEBERG_TOKEN }}
           UV_TEST_PUBLISH_CLOUDSMITH_TOKEN: ${{ secrets.UV_TEST_PUBLISH_CLOUDSMITH_TOKEN }}
+          UV_TEST_PUBLISH_PYTHON_VERSION: ${{ env.PYTHON_VERSION }}
 
   cache-test-ubuntu:
     timeout-minutes: 10