Fix CI failing due to Python version (#325)

Author: TwistedTwigleg

.github/workflows/ci.yml

@@ -15,15 +15,15 @@ env:
 
 jobs:
   unit-tests:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     strategy:
       fail-fast: false
 
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-python@v2
         with:
-          python-version: '3.6'
+          python-version: '3.6.7'
       - name: Unit tests
         run: |
           python3 setup.py install
@@ -49,4 +49,4 @@ jobs:
           pip install pytest
           pip install mock
           pip install boto3
-          ./test-integration/run/run.sh ${{ matrix.test-type }} 1000 100 7
+          ./test-integration/run/run.sh ${{ matrix.test-type }} 1000 100 7