Suppress underscore error and update valid CF version (#132)

* suppress inclusion of CF checker errors in short_summary.txt related to leading underscores in attribute name

* Update Python version from 3.6 to 3.8 in GitHub Actions

* Correct flake8 linter errors

* changed pytest.yml to be compatible with the Node.js 20 environment

* removed another linter error

* removed another linter error

* updated valid CF versions in run_checks.py

run_checks.py

@@ -50,7 +50,7 @@ def main():
     # Define version of CF table against which the files shall be checked.
     # Default is auto --> CF table version parsed from global attribute 'Conventions'.
     if cfversion != 'auto':
-        if cfversion not in ('1.4', '1.5', '1.6', '1.7', '1.8'):
+        if cfversion not in ('1.4', '1.5', '1.6', '1.7', '1.8', '1.9', '1.10', '1.11'):
             print('User-defined -cfv option invalid; using \'auto\' instead')
             cfversion = 'auto'