[wallet] encryptwallet should fail for watch-only wallet #15635
Description
Create a wallet as follows:
$ bitcoin-cli createwallet "watchonly" true
$ bitcoin-cli -rpcwallet=watchonly getwalletinfo
{
...
"private_keys_enabled": false
}The following should fail, but doesn't:
$ 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.