serializers.py

from django.contrib.auth.models import User
from django.utils.translation import ugettext as _

from rest_framework import serializers

class UserSerializer(serializers.ModelSerializer):
    password2 = serializers.CharField()

    class Meta:
        model = User
        fields = ('username', 'password', 'password2')

    def validate_password2(self, attrs, source):
        if attrs.get('password') == attrs.pop('password2'):
            return attrs
        raise serializers.ValidationError(
            _("The two password fields didn't match."),
            code='password_mismatch',
        )   

test.pytb

$ ./manage.py shell 
Python 2.7.3 (default, Sep 26 2013, 20:03:06) 
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
>>> from app.serializers import *
>>> u=UserSerializer(data={'username':'test1','password':'pass','password2':'pas'})
>>> u.errors
{'password2': [u"The two password fields didn't match."]}
>>> u=UserSerializer(data={'username':'test1','password':'pass','password2':'pass'})
>>> u.errors
{}
>>> u.data
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/home/han/.virtualenvs/drf_test/local/lib/python2.7/site-packages/rest_framework/serializers.py", line 537, in data
    self._data = self.to_native(obj)
  File "/home/han/.virtualenvs/drf_test/local/lib/python2.7/site-packages/rest_framework/serializers.py", line 325, in to_native
    value = field.field_to_native(obj, field_name)
  File "/home/han/.virtualenvs/drf_test/local/lib/python2.7/site-packages/rest_framework/fields.py", line 198, in field_to_native
    value = get_component(value, component)
  File "/home/han/.virtualenvs/drf_test/local/lib/python2.7/site-packages/rest_framework/fields.py", line 56, in get_component
    val = getattr(obj, attr_name)
AttributeError: 'User' object has no attribute 'password2'
>>>