MAINT pin python version for source tarball builder [cd build] (#21386)

ogrisel · glemaitre · commit bda53434321f · 2021-10-25T11:37:00.000+02:00
diff --git a/.github/workflows/wheels.yml b/.github/workflows/wheels.yml
@@ -124,6 +124,8 @@ jobs:
 
       - name: Setup Python
         uses: actions/setup-python@v2
+        with:
+          python-version: '3.9'  # update once build dependencies are available
 
       - name: Build source distribution
         run: bash build_tools/github/build_source.sh
