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
"}\n"
                },
                RPCExamples{
            "\nAdd a multisig address from 2 addresses\n"
            + HelpExampleCli("addmultisigaddress", "2 \"[\\\"16sSauSf5pF2UkUwvKGq4qjNRzBZYqgEL5\\\",\\\"171sgjn4YtPu27adkKGrdDwzRTxnRkBfKV\\\"]\"") +
            "\nAs a JSON-RPC call\n"
            + HelpExampleRpc("addmultisigaddress", "2, \"[\\\"16sSauSf5pF2UkUwvKGq4qjNRzBZYqgEL5\\\",\\\"171sgjn4YtPu27adkKGrdDwzRTxnRkBfKV\\\"]\"")
                },
            }.ToString();
        throw std::runtime_error(msg);
    }
    auto locked_chain = pwallet->chain().lock();
    LOCK(pwallet->cs_wallet);
    std::string label;
    if (!request.params[2].isNull())
        label = LabelFromValue(request.params[2]);
    int required = request.params[0].get_int();
    
    const UniValue& keys_or_addrs = request.params[1].get_array();
    std::vector<CPubKey> pubkeys;
    for (unsigned int i = 0; i < keys_or_addrs.size(); ++i) {
        if (IsHex(keys_or_addrs[i].get_str()) && (keys_or_addrs[i].get_str().length() == 66 || keys_or_addrs[i].get_str().length() == 130)) {
            pubkeys.push_back(HexToPubKey(keys_or_addrs[i].get_str()));
        } else {
            pubkeys.push_back(AddrToPubKey(pwallet, keys_or_addrs[i].get_str()));
        }
    }
    OutputType output_type = pwallet->m_default_address_type;
    if (!request.params[3].isNull()) {
        if (!ParseOutputType(request.params[3].get_str(), output_type)) {