text: Title: Unable to log in with the authentication information provided
  Body: when i post data, i always get this msg: Unable to log in with the authentication information provided
  
  ```
  class CustomBackend(ModelBackend):
      def authenticate(self, username=None, password=None, **kwargs):
          try:
              user = User.objects.get(Q(username=username)|Q(mobile=username))
              if user.check_password(password):
                  return user
          except Exception as e:
              return None
  ```
  ![xshot-0005](https://user-images.githubusercontent.com/15871933/49490467-2e8dfd00-f88b-11e8-96b7-22652ed3ddab.png)
  
  i'm follow offical website config, but don't know why not post data to API?