Cover vm_manager_cluster and get the main gate back to green

sonar-project.properties

@@ -11,6 +11,16 @@ sonar.sources=.
 sonar.exclusions=tests/**, docs/_build/**, htmlcov/**
 sonar.tests=tests
 
+# Code no test can execute, so counting it as uncovered says nothing.
+# vm_manager/helpers/tests holds the integration scripts driven by hand
+# against a real cluster; pyproject.toml already omits them from the
+# coverage run with the same reasoning, and this keeps SonarCloud in
+# step. conf.py and setup.py are build entry points.
+#
+# Coverage only: these files stay analysed, so the issues they carry
+# keep being reported.
+sonar.coverage.exclusions=vm_manager/helpers/tests/**, docs/conf.py, setup.py
+
 sonar.python.version=3.8, 3.9, 3.10, 3.11, 3.12
 
 # Written by the "Run tests" step of .github/workflows/ci.yml. Automatic