Cap python version

Author: Inbal Tako

.github/workflows/ci.yml

@@ -26,7 +26,7 @@ jobs:
     - name: Set up Python
       uses: actions/setup-python@v2
       with:
-        python-version: '3.x'
+        python-version: '3.7'
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip

.github/workflows/publish.yml

@@ -23,7 +23,7 @@ jobs:
     - name: Set up Python
       uses: actions/setup-python@v2
       with:
-        python-version: '3.x'
+        python-version: '3.7'
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip