Merge #17070: wallet: Avoid showing GUI popups on RPC errors

facec1c643 wallet: Avoid showing GUI popups on RPC errors (MarcoFalke)

Pull request description:

  RPC errors and warnings are shown as popups in the GUI instead of being returned to the RPC caller. For example,

  ```
  $ ./src/bitcoin-cli loadwallet $(pwd)/./test/functional/data/wallets/high_minversion/
  error code: -4
  error message:
  Wallet loading failed.
  ```

  gives me a GUI popup and no reason why loading the wallet failed.

  After this pull request:

  ```
  $ ./src/bitcoin-cli loadwallet $(pwd)/./test/functional/data/wallets/high_minversion/
  error code: -4
  error message:
  Wallet loading failed: Error loading /home/marco/workspace/btc_bitcoin_core/./test/functional/data/wallets/high_minversion/wallet.dat: Wallet requires newer version of Bitcoin Core

ACKs for top commit:
  laanwj:
    Code review ACK facec1c643

Tree-SHA512: c8274bbb02cfcf71676eeec1e773e51fb3538cf93f82e7cb8536f4716d44ed819cdc162dfc039ac7386a4db381a734cdb27fd32567043a1180c02519fbcba194

test/functional/wallet_multiwallet.py

@@ -339,14 +339,10 @@ class MultiWalletTest(BitcoinTestFramework):
         self.log.info("Fail -upgradewallet that results in downgrade")
         assert_raises_rpc_error(
             -4,
-            "Wallet loading failed.",
+            'Wallet loading failed: Error loading {}: Wallet requires newer version of {}'.format(
+                wallet_dir('high_minversion', 'wallet.dat'), self.config['environment']['PACKAGE_NAME']),
             lambda: self.nodes[0].loadwallet(filename='high_minversion'),
         )
-        self.stop_node(
-            i=0,
-            expected_stderr='Error: Error loading {}: Wallet requires newer version of Bitcoin Core'.format(
-                wallet_dir('high_minversion', 'wallet.dat')),
-        )
 
 
 if __name__ == '__main__':