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
"  \"fee\" : fee                     (numeric, optional) The transaction fee paid. Shown only if all UTXO slots in the PSBT have been filled.\n"
                "  \"next\" : \"role\"                 (string) Role of the next person that this psbt needs to go to\n"
                "}\n"
            },
            RPCExamples {
                HelpExampleCli("analyzepsbt", "\"psbt\"")
            }}.ToString());
    }
    RPCTypeCheck(request.params, {UniValue::VSTR});
    
    PartiallySignedTransaction psbtx;
    std::string error;
    if (!DecodeBase64PSBT(psbtx, request.params[0].get_str(), error)) {
        throw JSONRPCError(RPC_DESERIALIZATION_ERROR, strprintf("TX decode failed %s", error));
    }
    PSBTAnalysis psbta = AnalyzePSBT(psbtx);
    UniValue result(UniValue::VOBJ);
    UniValue inputs_result(UniValue::VARR);
    for (const auto& input : psbta.inputs) {
        UniValue input_univ(UniValue::VOBJ);
        UniValue missing(UniValue::VOBJ);
        input_univ.pushKV("has_utxo", input.has_utxo);
        input_univ.pushKV("is_final", input.is_final);
        input_univ.pushKV("next", PSBTRoleName(input.next));
        if (!input.missing_pubkeys.empty()) {
            UniValue missing_pubkeys_univ(UniValue::VARR);
            for (const CKeyID& pubkey : input.missing_pubkeys) {
                missing_pubkeys_univ.push_back(HexStr(pubkey));
            }
            missing.pushKV("pubkeys", missing_pubkeys_univ);