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
{
                    {"txid", RPCArg::Type::STR_HEX, RPCArg::Optional::NO, "The transaction id"},
                    {"verbose", RPCArg::Type::BOOL,  "false", "If false, return a string, otherwise return a json object"},
                    {"blockhash", RPCArg::Type::STR_HEX, RPCArg::Optional::OMITTED_NAMED_ARG, "The block in which to look for the transaction"},
                },
                {
                    RPCResult{"if verbose is not set or set to false",
            "\"data\"      (string) The serialized, hex-encoded data for 'txid'\n"
                     },
                     RPCResult{"if verbose is set to true",
            "{\n"
            "  \"in_active_chain\": b, (bool) Whether specified block is in the active chain or not (only present with explicit \"blockhash\" argument)\n"
            "  \"hex\" : \"data\",       (string) The serialized, hex-encoded data for 'txid'\n"
            "  \"txid\" : \"id\",        (string) The transaction id (same as provided)\n"
            "  \"hash\" : \"id\",        (string) The transaction hash (differs from txid for witness transactions)\n"
            "  \"size\" : n,             (numeric) The serialized transaction size\n"
            "  \"vsize\" : n,            (numeric) The virtual transaction size (differs from size for witness transactions)\n"
            "  \"weight\" : n,           (numeric) The transaction's weight (between vsize*4-3 and vsize*4)\n"
            "  \"version\" : n,          (numeric) The version\n"
            "  \"locktime\" : ttt,       (numeric) The lock time\n"
            "  \"vin\" : [               (array of json objects)\n"
            "     {\n"
            "       \"txid\": \"id\",    (string) The transaction id\n"
            "       \"vout\": n,         (numeric) \n"
            "       \"scriptSig\": {     (json object) The script\n"
            "         \"asm\": \"asm\",  (string) asm\n"
            "         \"hex\": \"hex\"   (string) hex\n"
            "       },\n"
            "       \"sequence\": n      (numeric) The script sequence number\n"
            "       \"txinwitness\": [\"hex\", ...] (array of string) hex-encoded witness data (if any)\n"