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 (request.fHelp || request.params.size() > 2) {
        throw std::runtime_error(
            RPCHelpMan{"sethdseed",
                "\nSet or generate a new HD wallet seed. Non-HD wallets will not be upgraded to being a HD wallet. Wallets that are already\n"
                "HD will have a new HD seed set so that new keys added to the keypool will be derived from this new seed.\n"
                "\nNote that you will need to MAKE A NEW BACKUP of your wallet after setting the HD wallet seed." +
                    HelpRequiringPassphrase(pwallet) + "\n",
                {
                    {"newkeypool", RPCArg::Type::BOOL,  "true", "Whether to flush old unused addresses, including change addresses, from the keypool and regenerate it.\n"
            "                             If true, the next address from getnewaddress and change address from getrawchangeaddress will be from this new seed.\n"
            "                             If false, addresses (including change addresses if the wallet already had HD Chain Split enabled) from the existing\n"
            "                             keypool will be used until it has been depleted."},
                    {"seed", RPCArg::Type::STR,  "random seed", "The WIF private key to use as the new HD seed.\n"
            "                             The seed value can be retrieved using the dumpwallet command. It is the private key marked hdseed=1"},
                },
                RPCResults{},
                RPCExamples{
                    HelpExampleCli("sethdseed", "")
            + HelpExampleCli("sethdseed", "false")
            + HelpExampleCli("sethdseed", "true \"wifkey\"")
            + HelpExampleRpc("sethdseed", "true, \"wifkey\"")
                },
            }.ToString());
    }
    if (pwallet->chain().isInitialBlockDownload()) {
        throw JSONRPCError(RPC_CLIENT_IN_INITIAL_DOWNLOAD, "Cannot set a new HD seed while still in Initial Block Download");
    }
    if (pwallet->IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS)) {
        throw JSONRPCError(RPC_WALLET_ERROR, "Cannot set a HD seed to a wallet with private keys disabled");