grab dependencies in sdist build
diff --git a/.github/workflows/build_wheels.yml b/.github/workflows/build_wheels.yml
index 59d099f..3f2d298 100644
--- a/.github/workflows/build_wheels.yml
+++ b/.github/workflows/build_wheels.yml
@@ -26,6 +26,9 @@
         with:
           python-version: '3.8'
 
+      - name: Install Python dependencies
+        run: python -m pip install --upgrade pip setuptools numpy tox pytest build
+
       - name: Build sdist
         run: python setup.py sdist