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
}
        if (!input.missing_redeem_script.IsNull()) {
            missing.pushKV("redeemscript", HexStr(input.missing_redeem_script));
        }
        if (!input.missing_witness_script.IsNull()) {
            missing.pushKV("witnessscript", HexStr(input.missing_witness_script));
        }
        if (!input.missing_sigs.empty()) {
            UniValue missing_sigs_univ(UniValue::VARR);
            for (const CKeyID& pubkey : input.missing_sigs) {
                missing_sigs_univ.push_back(HexStr(pubkey));
            }
            missing.pushKV("signatures", missing_sigs_univ);
        }
        if (!missing.getKeys().empty()) {
            input_univ.pushKV("missing", missing);
        }
        inputs_result.push_back(input_univ);
    }
    result.pushKV("inputs", inputs_result);
    if (psbta.estimated_vsize != nullopt) {
        result.pushKV("estimated_vsize", (int)*psbta.estimated_vsize);
    }
    if (psbta.estimated_feerate != nullopt) {
        result.pushKV("estimated_feerate", ValueFromAmount(psbta.estimated_feerate->GetFeePerK()));
    }
    if (psbta.fee != nullopt) {
        result.pushKV("fee", ValueFromAmount(*psbta.fee));
    }
    result.pushKV("next", PSBTRoleName(psbta.next));