Change authentification error message text - google-data-studio

Question

I've followed the guide error-handling for handling back an error to the users from the setCredentials method. However, even when using the provided example method to throw an error to the user, I still get the generic error on all my reports:
This is the default code I used for setting up the setCredentials function looker-studio auth connector.
function setCredentials(request) {
try {
Logger.log('setCredentials/try');
var creds = request.userPass;
var username = creds.username;
var password = creds.password;
var validCreds = validateCredentials(username, password).validCreds;
if (!validCreds) {
return {
errorCode: 'INVALID_CREDENTIALS'
};
};
var userProperties = PropertiesService.getUserProperties();
userProperties.setProperty('connector.username', username);
userProperties.setProperty('connector.password', password);
return {
errorCode: 'NONE'
};
} catch(e) {
Logger.log('setCredentials/catch');
DataStudioApp.createCommunityConnector()
.newUserError()
.setDebugText('Error setting credentials. Exception details: ' + e)
.setText('I want to show a custom error message')
.throwException();
}
}
This is the toast message I want to change
I tried to throw an error before returning INVALID_CREDENTIALS so it falls in the catch. However, I don't see changes in the text.
function setCredentials(request) {
try {
Logger.log('setCredentials/try');
var creds = request.userPass;
var username = creds.username;
var password = creds.password;
var validCreds = validateCredentials(username, password).validCreds;
if (!validCreds) {
throw new Error('Only to fall to the catch');
};
var userProperties = PropertiesService.getUserProperties();
userProperties.setProperty('connector.username', username);
userProperties.setProperty('connector.password', password);
return {
errorCode: 'NONE'
};
} catch(e) {
Logger.log('setCredentials/catch');
throw new Error('This message appears but it doesn't overwritte the default message');
}
}
(I have admin set to true)
If I throw again a new Error in the catch before the DataStudioApp newUserError I can see that 2 error toasts appear. A default one and mine, however this is not the intended result. What I want is to edit the default error message and I don't know if it's possible.