PhoneAuthError
interface
A custom error in the event verifying a phone number failed.
Example
firebase.auth().verifyPhoneNumber('+4423456789')
 .on('state_changed', (phoneAuthSnapshot) => {
   console.log('Snapshot state: ', phoneAuthSnapshot.state);
 }, (phoneAuthError) => {
   console.error('Error: ', phoneAuthError.message);
 });
