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.  
+ HelpExampleCli("listunspent", "6 9999999 '[]' true '{ \"minimumAmount\": 0.005 }'")
            + HelpExampleRpc("listunspent", "6, 9999999, [] , true, { \"minimumAmount\": 0.005 } ")
                },
            }.ToString());
    int nMinDepth = 1;
    if (!request.params[0].isNull()) {
        RPCTypeCheckArgument(request.params[0], UniValue::VNUM);
        nMinDepth = request.params[0].get_int();
    }
    int nMaxDepth = 9999999;
    if (!request.params[1].isNull()) {
        RPCTypeCheckArgument(request.params[1], UniValue::VNUM);
        nMaxDepth = request.params[1].get_int();
    }
    std::set<CTxDestination> destinations;
    if (!request.params[2].isNull()) {
        RPCTypeCheckArgument(request.params[2], UniValue::VARR);
        UniValue inputs = request.params[2].get_array();
        for (unsigned int idx = 0; idx < inputs.size(); idx++) {
            const UniValue& input = inputs[idx];
            CTxDestination dest = DecodeDestination(input.get_str());
            if (!IsValidDestination(dest)) {
                throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, std::string("Invalid Bitcoin address: ") + input.get_str());
            }
            if (!destinations.insert(dest).second) {
                throw JSONRPCError(RPC_INVALID_PARAMETER, std::string("Invalid parameter, duplicated address: ") + input.get_str());
            }
        }
    }
    bool include_unsafe = true;