Merge pull request #125 from transifex/update_ci_python_version

Update python version 3.7 at ci pipeline

Author: deathbird

.github/workflows/ci.yml

@@ -103,10 +103,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
-      - name: Set up Python 3.7
+      - name: Set up Python 3.9
         uses: actions/setup-python@v1
         with:
-          python-version: 3.7
+          python-version: 3.9
       - name: Build source tarball
         run: python setup.py sdist
       - name: Publish package