wallet: Display non-HD error on first run

test/functional/wallet-hd.py

@@ -20,6 +20,12 @@ class WalletHDTest(BitcoinTestFramework):
     def run_test (self):
         tmpdir = self.options.tmpdir
 
+        # Make sure can't switch off usehd after wallet creation
+        self.stop_node(1)
+        self.assert_start_raises_init_error(1, ['-usehd=0'], 'already existing HD wallet')
+        self.start_node(1)
+        connect_nodes_bi(self.nodes, 0, 1)
+
         # Make sure we use hd, keep masterkeyid
         masterkeyid = self.nodes[1].getwalletinfo()['hdmasterkeyid']
         assert_equal(len(masterkeyid), 40)