Update CI/CD to use Python 3 (untested)

Author: mesozoic

.github/workflows/continuous-integration.yml

@@ -19,7 +19,7 @@ jobs:
     - name: Set up Python ${{ matrix.python-version }}
       uses: actions/setup-python@v2
       with:
-        python-version: 2.7
+        python-version: 3.8
 
     - name: Install test dependencies
       run: |

.travis.yml

@@ -4,9 +4,7 @@ osx_image: xcode8.3
 
 env:
   matrix:
-    - VERSION=2.7.10 SOURCE=macpython
-    # Turn off 2.6 as it's no longer supported
-    # - VERSION=2.6.9 SOURCE=macports
+    - VERSION=3.8.9 SOURCE=macpython
 
 before_install:
   # - brew update