old_contents: from django.contrib.auth import authenticate
  from rest_framework import serializers
  
  
  class AuthTokenSerializer(serializers.Serializer):
      username = serializers.CharField()
      password = serializers.CharField()
  
      def validate(self, attrs):
          username = attrs.get('username')
          password = attrs.get('password')
  
          if username and password:
              user = authenticate(username=username, password=password)
  
              if user:
                  if not user.is_active:
                      raise serializers.ValidationError('User account is disabled.')
                  attrs['user'] = user
                  return attrs
              else:
                  raise serializers.ValidationError('Unable to login with provided credentials.')
          else:
              raise serializers.ValidationError('Must include "username" and "password"')
  
new_contents: from django.contrib.auth import authenticate
  from django.utils.translation import ugettext_lazy as _
  
  from rest_framework import serializers
  
  
  class AuthTokenSerializer(serializers.Serializer):
      username = serializers.CharField()
      password = serializers.CharField()
  
      def validate(self, attrs):
          username = attrs.get('username')
          password = attrs.get('password')
  
          if username and password:
              user = authenticate(username=username, password=password)
  
              if user:
                  if not user.is_active:
                      msg = _('User account is disabled.')
                      raise serializers.ValidationError()
                  attrs['user'] = user
                  return attrs
              else:
                  msg = _('Unable to login with provided credentials.')
                  raise serializers.ValidationError(msg)
          else:
              msg = _('Must include "username" and "password"')
              raise serializers.ValidationError(msg)
  
subject: Mark strings in AuthTokenSerializer as translatable