Restore original task in test_warning_logs (#17985)

Co-authored-by: ydshieh <ydshieh@users.noreply.github.com>

tests/pipelines/test_pipelines_common.py

@@ -777,9 +777,17 @@ class PipelineRegistryTest(unittest.TestCase):
         logger_ = transformers_logging.get_logger("transformers.pipelines.base")
 
         alias = "text-classification"
-        with CaptureLogger(logger_) as cm:
-            PIPELINE_REGISTRY.register_pipeline(alias, {})
-        self.assertIn(f"{alias} is already registered", cm.out)
+        # Get the original task, so we can restore it at the end.
+        # (otherwise the subsequential tests in `TextClassificationPipelineTests` will fail)
+        original_task, original_task_options = PIPELINE_REGISTRY.check_task(alias)
+
+        try:
+            with CaptureLogger(logger_) as cm:
+                PIPELINE_REGISTRY.register_pipeline(alias, {})
+            self.assertIn(f"{alias} is already registered", cm.out)
+        finally:
+            # restore
+            PIPELINE_REGISTRY.register_pipeline(alias, original_task)
 
     @require_torch
     def test_register_pipeline(self):