travis run: https://travis-ci.org/bitcoin/bitcoin/jobs/406813397

```
rpc_psbt.py failed, Duration: 4 s
stdout:
2018-07-22T13:28:57.765000Z TestFramework (INFO): Initializing test directory /tmp/bitcoin_test_runner_20180722_132530/rpc_psbt_49
2018-07-22T13:29:00.531000Z TestFramework (ERROR): Assertion failed
Traceback (most recent call last):
  File "/home/travis/build/bitcoin/bitcoin/build/bitcoin-x86_64-unknown-linux-gnu/test/functional/test_framework/test_framework.py", line 160, in main
    self.run_test()
  File "/home/travis/build/bitcoin/bitcoin/build/bitcoin-x86_64-unknown-linux-gnu/test/functional/rpc_psbt.py", line 101, in run_test
    assert_raises_rpc_error(-22, "TX decode failed", self.nodes[0].converttopsbt, signedtx['hex'])
  File "/home/travis/build/bitcoin/bitcoin/build/bitcoin-x86_64-unknown-linux-gnu/test/functional/test_framework/util.py", line 105, in assert_raises_rpc_error
    assert try_rpc(code, message, fun, *args, **kwds), "No exception raised"
AssertionError: No exception raised
flags |= WALLET_FLAG_BLANK_WALLET;
    }
    WalletLocation location(request.params[0].get_str());
    if (location.Exists()) {
        throw JSONRPCError(RPC_WALLET_ERROR, "Wallet " + location.GetName() + " already exists.");
    }
    
    if (!CWallet::Verify(*g_rpc_interfaces->chain, location, false, error, warning)) {
        throw JSONRPCError(RPC_WALLET_ERROR, "Wallet file verification failed: " + error);
    }
    std::shared_ptr<CWallet> const wallet = CWallet::CreateWalletFromFile(*g_rpc_interfaces->chain, location, flags);
    if (!wallet) {
        throw JSONRPCError(RPC_WALLET_ERROR, "Wallet creation failed.");
    }
    AddWallet(wallet);
    wallet->postInitProcess();
    UniValue obj(UniValue::VOBJ);
    obj.pushKV("name", wallet->GetName());
    obj.pushKV("warning", warning);
    return obj;
}
static UniValue unloadwallet(const JSONRPCRequest& request)
{
    if (request.fHelp || request.params.size() > 1) {
        throw std::runtime_error(
            RPCHelpMan{"unloadwallet",
                "Unloads the wallet referenced by the request endpoint otherwise unloads the wallet specified in the argument.\n"
                "Specifying the wallet name on a wallet endpoint is invalid.",
                {
                    {"wallet_name", RPCArg::Type::STR,  "the wallet name from the RPC request", "The name of the wallet to unload."},