fix: test_server_errors mock fix for failed CI

For the success case, return None for usage not a mock object.

Signed-off-by: Mark Sturdevant <mark.sturdevant@ibm.com>

Author: markstur

test/cli/test_serve_errors.py

@@ -17,6 +17,7 @@ def mock_module_success():
     module.__name__ = "test_module"
     output = Mock()
     output.value = "Test response"
+    output.usage = None  # No usage info in this test
     module.serve = Mock(return_value=output)
     return module