gh-75459: Doc: Tell sphinx to run graphviz

Author: rhansen

.github/workflows/reusable-docs.yml

@@ -80,6 +80,12 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 60
     steps:
+    - name: 'Install Dependencies'
+      run: |
+        sudo apt-get update &&
+        sudo env DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends \
+            graphviz \
+            ;
     - uses: actions/checkout@v4
     - name: 'Set up Python'
       uses: actions/setup-python@v5

.readthedocs.yml

@@ -11,25 +11,26 @@ build:
   os: ubuntu-24.04
   tools:
     python: "3"
+  apt_packages:
+    - graphviz
+  jobs:
+    post_checkout:
+      # https://docs.readthedocs.io/en/stable/build-customization.html#cancel-build-based-on-a-condition
+      #
+      # Cancel building pull requests when there aren't changes in the Doc directory.
+      #
+      # If there are no changes (git diff exits with 0) we force the command to return with 183.
+      # This is a special exit code on Read the Docs that will cancel the build immediately.
+      - |
+        if [ "$READTHEDOCS_VERSION_TYPE" = "external" ] && [ "$(git diff --quiet origin/main -- Doc/ .readthedocs.yml; echo $?)" -eq 0 ];
+        then
+          echo "No changes to Doc/ - exiting the build.";
+          exit 183;
+        fi
 
-  commands:
-    # https://docs.readthedocs.io/en/stable/build-customization.html#cancel-build-based-on-a-condition
-    #
-    # Cancel building pull requests when there aren't changes in the Doc directory.
-    #
-    # If there are no changes (git diff exits with 0) we force the command to return with 183.
-    # This is a special exit code on Read the Docs that will cancel the build immediately.
-    - |
-      if [ "$READTHEDOCS_VERSION_TYPE" = "external" ] && [ "$(git diff --quiet origin/main -- Doc/ .readthedocs.yml; echo $?)" -eq 0 ];
-      then
-        echo "No changes to Doc/ - exiting the build.";
-        exit 183;
-      fi
-
-    - asdf plugin add uv
-    - asdf install uv latest
-    - asdf global uv latest
-    - make -C Doc venv html
-    - mkdir _readthedocs
-    - mv Doc/build/html _readthedocs/html
-
+      - asdf plugin add uv
+      - asdf install uv latest
+      - asdf global uv latest
+      - make -C Doc venv html
+      - mkdir _readthedocs
+      - mv Doc/build/html _readthedocs/html