Create a wallet as follows:

```sh
$ bitcoin-cli createwallet "watchonly" true
$ bitcoin-cli -rpcwallet=watchonly getwalletinfo
{
   ...
   "private_keys_enabled": false
}
```

The following should fail, but doesn't:

```sh
$ bitcoin-cli -rpcwallet=watchonly encryptwallet 1234
wallet encrypted; The keypool has been flushed and a new HD seed was generated (if you are using HD). You need to make a new backup.
```

It partially fails silently, because it doesn't actually add a seed. But it does ask for a password when calling `dumpwallet`, which doesn't make sense because we currently don't encrypt anything other than private keys.  
{"estimate_mode", RPCArg::Type::STR,  "UNSET", "The fee estimate mode, must be one of:\n"
                            "         \"UNSET\"\n"
                            "         \"ECONOMICAL\"\n"
                            "         \"CONSERVATIVE\""},
                        },
                        "options"},
                    {"bip32derivs", RPCArg::Type::BOOL,  "false", "If true, includes the BIP 32 derivation paths for public keys if we know them"},
                },
                RPCResult{
                            "{\n"
                            "  \"psbt\": \"value\",        (string)  The resulting raw transaction (base64-encoded string)\n"
                            "  \"fee\":       n,         (numeric) Fee in " + CURRENCY_UNIT + " the resulting transaction pays\n"
                            "  \"changepos\": n          (numeric) The position of the added change output, or -1\n"
                            "}\n"
                                },
                                RPCExamples{
                            "\nCreate a transaction with no inputs\n"
                            + HelpExampleCli("walletcreatefundedpsbt", "\"[{\\\"txid\\\":\\\"myid\\\",\\\"vout\\\":0}]\" \"[{\\\"data\\\":\\\"00010203\\\"}]\"")
                                },
                            }.ToString());
    RPCTypeCheck(request.params, {
        UniValue::VARR,
        UniValueType(), 
        UniValue::VNUM,
        UniValue::VOBJ,
        UniValue::VBOOL
        }, true
    );
    CAmount fee;
    int change_position;