title: Recognize user who has signed up with Google but tries to sign in with email in AWS Cognito
body: <p>I'm using AWS Cognito Federated Identities to enable social login with Google in a web app.</p>
  <p>Attempts:</p>
  <ol>
  <li>User (with email foo@gmail.com) signin/signup by Google</li>
  <li>User login by email foo@gmail.com</li>
  </ol>
  <p>Normal behavior: In the 2nd attempt, user will get an error <em>UserNotFoundException</em></p>
  <p>Expected response: my web will inform user, that he should login by google</p>