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
},
                RPCResults{},
                RPCExamples{
                    HelpExampleCli("walletpassphrasechange", "\"old one\" \"new one\"")
            + HelpExampleRpc("walletpassphrasechange", "\"old one\", \"new one\"")
                },
            }.ToString());
    }
    auto locked_chain = pwallet->chain().lock();
    LOCK(pwallet->cs_wallet);
    if (!pwallet->IsCrypted()) {
        throw JSONRPCError(RPC_WALLET_WRONG_ENC_STATE, "Error: running with an unencrypted wallet, but walletpassphrasechange was called.");
    }
    
    
    SecureString strOldWalletPass;
    strOldWalletPass.reserve(100);
    strOldWalletPass = request.params[0].get_str().c_str();
    SecureString strNewWalletPass;
    strNewWalletPass.reserve(100);
    strNewWalletPass = request.params[1].get_str().c_str();
    if (strOldWalletPass.empty() || strNewWalletPass.empty()) {
        throw JSONRPCError(RPC_INVALID_PARAMETER, "passphrase can not be empty");
    }
    if (!pwallet->ChangeWalletPassphrase(strOldWalletPass, strNewWalletPass)) {
        throw JSONRPCError(RPC_WALLET_PASSPHRASE_INCORRECT, "Error: The wallet passphrase entered was incorrect.");
    }
    return NullUniValue;
}
static UniValue walletlock(const JSONRPCRequest& request)