datacarrier: deprecate startup arguments for future removal

test/functional/mempool_datacarrier.py

@@ -89,6 +89,17 @@ class DataCarrierTest(BitcoinTestFramework):
         self.test_null_data_transaction(node=self.nodes[2], data=one_byte, success=True)
         self.test_null_data_transaction(node=self.nodes[3], data=one_byte, success=False)
 
+        # Clean shutdown boilerplate due to deprecation
+        self.expected_stderr = [
+            "",  # node 0 has no deprecated options
+            "Warning: Options '-datacarrier' or '-datacarriersize' are set but are marked as deprecated. They will be removed in a future version.",
+            "Warning: Options '-datacarrier' or '-datacarriersize' are set but are marked as deprecated. They will be removed in a future version.",
+            "Warning: Options '-datacarrier' or '-datacarriersize' are set but are marked as deprecated. They will be removed in a future version.",
+        ]
+
+        for i in range(self.num_nodes):
+            self.stop_node(i, expected_stderr=self.expected_stderr[i])
+
 
 if __name__ == '__main__':
     DataCarrierTest(__file__).main()