install setuptools to ensure we aren't missing distutils

Author: drbenvincent

.github/workflows/ci.yml

@@ -19,6 +19,10 @@ jobs:
         uses: actions/setup-python@v3
         with:
           python-version: ${{ matrix.python-version }}
+      - name: Install setuptools
+        run: |
+          python -m ensurepip
+          pip install --upgrade pip setuptools
       - name: Run doctests
         run: |
           pip install -e .[test]