Build pypi tarball

Author: nbasili

.github/workflows/ci.yml

@@ -47,6 +47,12 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
+      - name: Set up Python 3.7
+        uses: actions/setup-python@v1
+        with:
+          python-version: 3.7
+      - name: Build source tarball
+        run: python setup.py sdist
       - name: Publish package
         uses: pypa/gh-action-pypi-publish@master
         with: