Work around build issues raised by Cython 3.0.0.

Signed-off-by: Jeff Licquia <[email protected]>

.github/workflows/validate_pull_request.yml

@@ -9,7 +9,9 @@ jobs:
     - uses: actions/checkout@v1
       with:
         fetch-depth: 1
+    - name: Install build requirements for pre-requisites
+      run: pip install -r build-requirements.txt
     - name: Install pre-requisites
-      run: pip install -r requirements.txt
+      run: pip install --no-build-isolation -r requirements.txt
     - name: Build
       run: mkdocs build -v --clean

build-requirements.txt

@@ -0,0 +1,3 @@
+setuptools
+wheel
+Cython<3.0