[BugFix][CI/Build][ROCM] Fix import error and apply assert in appropriate case in test_struct_output_generate (vllm-project#28311)

Signed-off-by: Randall Smith <ransmith@amd.com>
Co-authored-by: Randall Smith <ransmith@amd.com>
Signed-off-by: ernie-chang <ernie.chang@cienet.com>

Author: 2 people

tests/v1/entrypoints/llm/test_struct_output_generate.py

@@ -677,9 +677,14 @@ def test_structured_output_with_reasoning_matrices(
     reasoning, content = run_reasoning_extraction(reasoner, [generated_text])
     print(f"Prompt: {prompt!r}\nReasoning: {reasoning!r}\nContent: {content!r}")
 
-    assert content is not None and reasoning is not None
-    output_json = json.loads(content)
-    jsonschema.validate(instance=output_json, schema=reasoning_schema)
+    if "Qwen3" in model_name:
+        assert content is not None
+
+    assert reasoning is not None
+
+    if content is not None:
+        output_json = json.loads(content)
+        jsonschema.validate(instance=output_json, schema=reasoning_schema)
 
 
 @pytest.mark.skip_global_cleanup