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.  
};
static UniValue DescribeWalletAddress(CWallet* pwallet, const CTxDestination& dest)
{
    UniValue ret(UniValue::VOBJ);
    UniValue detail = DescribeAddress(dest);
    ret.pushKVs(detail);
    ret.pushKVs(boost::apply_visitor(DescribeWalletAddressVisitor(pwallet), dest));
    return ret;
}
static UniValue AddressBookDataToJSON(const CAddressBookData& data, const bool verbose)
{
    UniValue ret(UniValue::VOBJ);
    if (verbose) {
        ret.pushKV("name", data.name);
    }
    ret.pushKV("purpose", data.purpose);
    return ret;
}
UniValue getaddressinfo(const JSONRPCRequest& request)