Fix importmulti bug when importing an already imported key

src/wallet/rpcdump.cpp

@@ -961,7 +961,7 @@ UniValue ProcessImport(CWallet * const pwallet, const UniValue& data, const int6
                 pwallet->SetAddressBook(vchAddress, label, "receive");
 
                 if (pwallet->HaveKey(vchAddress)) {
-                    return false;
+                    throw JSONRPCError(RPC_WALLET_ERROR, "The wallet already contains the private key for this address or script");
                 }
 
                 pwallet->mapKeyMetadata[vchAddress].nCreateTime = timestamp;

test/functional/importmulti.py

@@ -160,6 +160,18 @@ class ImportMultiTest (BitcoinTestFramework):
         assert_equal(address_assert['ismine'], True)
         assert_equal(address_assert['timestamp'], timestamp)
 
+        self.log.info("Should not import an address with private key if is already imported")
+        result = self.nodes[1].importmulti([{
+            "scriptPubKey": {
+                "address": address['address']
+            },
+            "timestamp": "now",
+            "keys": [ self.nodes[0].dumpprivkey(address['address']) ]
+        }])
+        assert_equal(result[0]['success'], False)
+        assert_equal(result[0]['error']['code'], -4)
+        assert_equal(result[0]['error']['message'], 'The wallet already contains the private key for this address or script')
+
         # Address + Private key + watchonly
         self.log.info("Should not import an address with private key and with watchonly")
         address = self.nodes[0].validateaddress(self.nodes[0].getnewaddress())