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
"  \"complete\" : true|false,          (boolean) If the transaction has a complete set of signatures\n"
            "  \"errors\" : [                      (json array of objects) Script verification errors (if there are any)\n"
            "    {\n"
            "      \"txid\" : \"hash\",              (string) The hash of the referenced, previous transaction\n"
            "      \"vout\" : n,                   (numeric) The index of the output to spent and used as input\n"
            "      \"scriptSig\" : \"hex\",          (string) The hex-encoded signature script\n"
            "      \"sequence\" : n,               (numeric) Script sequence number\n"
            "      \"error\" : \"text\"              (string) Verification or signing error related to the input\n"
            "    }\n"
            "    ,...\n"
            "  ]\n"
            "}\n"
                },
                RPCExamples{
                    HelpExampleCli("signrawtransactionwithwallet", "\"myhex\"")
            + HelpExampleRpc("signrawtransactionwithwallet", "\"myhex\"")
                },
            }.ToString());
    RPCTypeCheck(request.params, {UniValue::VSTR, UniValue::VARR, UniValue::VSTR}, true);
    CMutableTransaction mtx;
    if (!DecodeHexTx(mtx, request.params[0].get_str(), true)) {
        throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "TX decode failed");
    }
    
    auto locked_chain = pwallet->chain().lock();
    LOCK(pwallet->cs_wallet);
    EnsureWalletIsUnlocked(pwallet);
    return SignTransaction(pwallet->chain(), mtx, request.params[1], pwallet, false, request.params[2]);
}
static UniValue bumpfee(const JSONRPCRequest& request)