Pin the action version (#19)

Author: pcothenet

Diff for: .github/workflows/publish.yml

@@ -14,7 +14,7 @@ jobs:
       - name: Setup Python
         uses: actions/setup-python@v2
         with:
-          python-version: '3.6'
+          python-version: "3.6"
 
       - name: Run tests
         env:
@@ -38,7 +38,7 @@ jobs:
           .
 
       - name: Publish a Python distribution to PyPI
-        uses: pypa/gh-action-pypi-publish@master
+        uses: pypa/gh-action-pypi-publish@release/v1.4.2
         with:
           user: __token__
           password: ${{ secrets.PYPI_API_TOKEN }}