class SignupByEmailSerializer(serializers.ModelSerializer):
    def create(self, validated_data):
        def __generate_username():
            username = get_random_string(
                length=8
            )
            try:
                SwishUser.objects.get(
                    username=username
                )
                return __generate_username()
            except SwishUser.DoesNotExist:
                return username

        user = SwishUser(
            email=validated_data['email'],
            username=__generate_username()
        )
        user.set_password(validated_data['password'])

        user.save()
        return user

    def validate(self, attrs):
        user = SwishUser(**attrs)

        password = attrs.get('password')

        errors = dict()
        try:
            password_validation.validate_password(
                password=password,
                user=user,
                password_validators=[
                    CommonPasswordValidator(),
                    MinimumLengthValidator(min_length=4)
                ]
            )
        except exceptions.ValidationError as e:
            errors['password'] = list(e.messages)

        if errors:
            raise serializers.ValidationError(errors)

        return super(SignupByEmailSerializer, self).validate(attrs)

    class Meta:
        model = SwishUser
        fields = ('email', 'password')
        fields = ('email',)
        extra_kwargs = {
            'password': {
                'write_only': True
            'email': {
                'required': True,
                'allow_null': False,
                'allow_blank': False
            }
        }