tests/functional: Mark main in QemuBaseTest class as a static method

The main() method in the QemuBaseTest class has no parameters but is
defined as a regular method. Currently, this does not cause any issues
because in the functional tests main() is always called directly from
QemuBaseTest (never from instances), but the way this method is defined
makes its signature wrong, implying a 'self'. Hence, it's best practice
to define such a method as a static method, so decorate it with
@staticmethod.

Signed-off-by: Gustavo Romero <gustavo.romero@linaro.org>
Message-ID: <20250819143916.4138035-4-gustavo.romero@linaro.org>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

tests/functional/qemu_test/testcase.py

@@ -235,6 +235,7 @@ class QemuBaseTest(unittest.TestCase):
         self.log.removeHandler(self._log_fh)
         self._log_fh.close()
 
+    @staticmethod
     def main():
         warnings.simplefilter("default")
         os.environ["PYTHONWARNINGS"] = "default"