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
}
    }
    
    
    pwallet->BlockUntilSyncedToCurrentChain();
    auto locked_chain = pwallet->chain().lock();
    LOCK(pwallet->cs_wallet);
    EnsureWalletIsUnlocked(pwallet);
    std::vector<std::string> errors;
    CAmount old_fee;
    CAmount new_fee;
    CMutableTransaction mtx;
    feebumper::Result res;
    if (totalFee > 0) {
        
        res = feebumper::CreateTotalBumpTransaction(pwallet, hash, coin_control, totalFee, errors, old_fee, new_fee, mtx);
    } else {
        
        res = feebumper::CreateRateBumpTransaction(pwallet, hash, coin_control, errors, old_fee, new_fee, mtx);
    }
    if (res != feebumper::Result::OK) {
        switch(res) {
            case feebumper::Result::INVALID_ADDRESS_OR_KEY:
                throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, errors[0]);
                break;
            case feebumper::Result::INVALID_REQUEST:
                throw JSONRPCError(RPC_INVALID_REQUEST, errors[0]);
                break;
            case feebumper::Result::INVALID_PARAMETER:
                throw JSONRPCError(RPC_INVALID_PARAMETER, errors[0]);