💚 setup python version for PyPi wf

.github/workflows/pypi.yml

@@ -14,6 +14,9 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
+      - uses: actions/setup-python@v2
+        with:
+          python-version: 3.7
       - uses: actions/cache@v2
         with:
           path: ~/.cache/pip