submitheader: more directly test missing prev block header

test/functional/mining_basic.py

@@ -166,7 +166,7 @@ class MiningTest(BitcoinTestFramework):
         self.log.info('submitheader tests')
         assert_raises_rpc_error(-22, 'Block header decode failed', lambda: node.submitheader(hexdata='xx' * BLOCK_HEADER_SIZE))
         assert_raises_rpc_error(-22, 'Block header decode failed', lambda: node.submitheader(hexdata='ff' * (BLOCK_HEADER_SIZE-2)))
-        assert_raises_rpc_error(-25, 'Must submit previous header', lambda: node.submitheader(hexdata='ff' * BLOCK_HEADER_SIZE))
+        assert_raises_rpc_error(-25, 'Must submit previous header', lambda: node.submitheader(hexdata=super(CBlock, bad_block).serialize().hex()))
 
         block.nTime += 1
         block.solve()