Django Rest Framework custom exception handling doesn't recognize parameter

I am following the answer to the question Django REST Framework how to specify error code when raising validation error in serializer in order to custom exception handling, but i get an error.

This is my custom exception handler:

from rest_framework.exceptions import APIException
from django.utils.encoding import force_text
from rest_framework import status

class CustomValidation(APIException):
    status_code = status.HTTP_500_INTERNAL_SERVER_ERROR
    default_detail = 'A server error ocurred'

    def __init__(self, detail, field, status_code):
        if status_code is not None:
            self.status_code = status_code
            if detail is not None:
                self.detail = {field: force_text(detail)}
            else:
                self.detail = {'detail': force_text(self.default_detail)}

This is where I raise the exception:

class UserSerializer(serializers.HyperlinkedModelSerializer):
    class Meta:
        model = User
        fields = ('id', 'username', 'first_name', 'last_name', 'email', 'password')

    def create(self, validated_data):
        try:
            user = models.User.objects.get(email=validated_data.get('email'))
        except User.DoesNotExist:
            user = models.User.objects.create(**validated_data)

            user.set_password(user.password)
            user.save()
            Token.objects.create(user=user)

            return user
        else:
            raise CustomValidation('eMail already in use', 'email', status_code=status.HTTP_409_CONFLICT)

And this is the traceback that I get:

Internal Server Error: /es/users_manager/users/
Traceback (most recent call last):
  File "/Users/hugovillalobos/Documents/Code/IntellibookProject/IntellibookVenv/lib/python3.6/site-packages/rest_framework/views.py", line 480, in dispatch
    response = handler(request, *args, **kwargs)
  File "/Users/hugovillalobos/Documents/Code/IntellibookProject/IntellibookVenv/lib/python3.6/site-packages/rest_framework/mixins.py", line 21, in create
    self.perform_create(serializer)
  File "/Users/hugovillalobos/Documents/Code/IntellibookProject/IntellibookVenv/lib/python3.6/site-packages/rest_framework/mixins.py", line 26, in perform_create
    serializer.save()
  File "/Users/hugovillalobos/Documents/Code/IntellibookProject/IntellibookVenv/lib/python3.6/site-packages/rest_framework/serializers.py", line 214, in save
    self.instance = self.create(validated_data)
  File "/Users/hugovillalobos/Documents/Code/IntellibookProject/Intellibook/UsersManagerApp/serializers.py", line 25, in create
    raise CustomValidation('eMail already in use', 'email', status_code=status.HTTP_409_CONFLICT)
GeneralApp.utils.CustomValidation: {'email': 'eMail already in use'}

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Users/hugovillalobos/Documents/Code/IntellibookProject/IntellibookVenv/lib/python3.6/site-packages/django/core/handlers/exception.py", line 35, in inner
    response = get_response(request)
  File "/Users/hugovillalobos/Documents/Code/IntellibookProject/IntellibookVenv/lib/python3.6/site-packages/django/core/handlers/base.py", line 128, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "/Users/hugovillalobos/Documents/Code/IntellibookProject/IntellibookVenv/lib/python3.6/site-packages/django/core/handlers/base.py", line 126, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/Users/hugovillalobos/Documents/Code/IntellibookProject/IntellibookVenv/lib/python3.6/site-packages/django/views/decorators/csrf.py", line 54, in wrapped_view
    return view_func(*args, **kwargs)
  File "/Users/hugovillalobos/Documents/Code/IntellibookProject/IntellibookVenv/lib/python3.6/site-packages/rest_framework/viewsets.py", line 103, in view
    return self.dispatch(request, *args, **kwargs)
  File "/Users/hugovillalobos/Documents/Code/IntellibookProject/IntellibookVenv/lib/python3.6/site-packages/rest_framework/views.py", line 483, in dispatch
    response = self.handle_exception(exc)
  File "/Users/hugovillalobos/Documents/Code/IntellibookProject/IntellibookVenv/lib/python3.6/site-packages/rest_framework/views.py", line 440, in handle_exception
    response = exception_handler(exc, context)
TypeError: __init__() missing 1 required positional argument: 'status_code'
[07/Jun/2018 02:42:16] "POST /es/users_manager/users/ HTTP/1.1" 500 102763

I don't know what I am missing.