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
for (const auto& sig : input.partial_sigs) {
                partial_sigs.pushKV(HexStr(sig.second.first), HexStr(sig.second.second));
            }
            in.pushKV("partial_signatures", partial_sigs);
        }
        
        if (input.sighash_type > 0) {
            in.pushKV("sighash", SighashToStr((unsigned char)input.sighash_type));
        }
        
        if (!input.redeem_script.empty()) {
            UniValue r(UniValue::VOBJ);
            ScriptToUniv(input.redeem_script, r, false);
            in.pushKV("redeem_script", r);
        }
        if (!input.witness_script.empty()) {
            UniValue r(UniValue::VOBJ);
            ScriptToUniv(input.witness_script, r, false);
            in.pushKV("witness_script", r);
        }
        
        if (!input.hd_keypaths.empty()) {
            UniValue keypaths(UniValue::VARR);
            for (auto entry : input.hd_keypaths) {
                UniValue keypath(UniValue::VOBJ);
                keypath.pushKV("pubkey", HexStr(entry.first));
                keypath.pushKV("master_fingerprint", strprintf("%08x", ReadBE32(entry.second.fingerprint)));
                keypath.pushKV("path", WriteHDKeypath(entry.second.path));
                keypaths.push_back(keypath);
            }