build: issue2551397: remove support for python 3.6

Try CI build on python 3.7. If this fails go to python 3.8 build.

Author: rouilj

.github/workflows/ci-test.yml

@@ -78,9 +78,9 @@ jobs:
             #  os: ubuntu-22.04
             #  experimental: true
 
-            # 3.6 not available on new 22.04 runners, so run on 20.04 ubuntu
-            - python-version: 3.6
-              os: ubuntu-20.04
+            # 3.7 not available on new 22.04 runners, so run on 22.04 ubuntu
+            - python-version: 3.7
+              os: ubuntu-22.04
 
             # 3.8 not available on new 24.04 runners, so run on 22.04 ubuntu
             - python-version: 3.8
@@ -303,10 +303,7 @@ jobs:
               -W "ignore:unclosed:ResourceWarning:roundup.roundup.demo" \
               -W "ignore:unclosed file:ResourceWarning:enum" \
               -v  test/ --cov=roundup
-            if [[ "$PYTHON_VERSION" != "3.6" ]]; then
-              # coverage before 3.6 doesn't support lcov output
               coverage lcov
-            fi
           else
             # python2 case
             pytest -v -r a --durations=20 test/ --cov=roundup