github: run tests with python3

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>

.github/workflows/main.yml

@@ -7,16 +7,15 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        hg: [ '5.0', '5.1', '5.2', '5.3', '5.4', '5.5', '5.6', '5.7' ]
+        hg: [ '5.5', '5.6', '5.7', '5.8', '5.9', '6.0', '6.1', '6.2' ]
     env:
       HG_VERSION: ${{ matrix.hg }}
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-python@v4
         with:
-          python-version: '2.7'
-      - name: Install python-dev
-        run: sudo apt-get install -y python2.7-dev
+          python-version: '3.8'
+          check-latest: true
       - name: Cache check-versions script
         id: cache-check-versions
         uses: actions/cache@v3