def validate(self, data):
        email = data.get('email', None)
        username = data.get('username', None)
        password = data.get('password', None)
        if email is None and username is None:
            raise serializers.ValidationError(
                error_messages['field required'].format('Email or Username'))
        if password is None:
            raise serializers.ValidationError(
                error_messages['field required'].format('Password'))
        if username is not None:
            try:
                user_object = User.objects.get(
                username=username.strip().lower())
                email =  user_object.email
            except User.DoesNotExist:
               raise serializers.ValidationError(
                   'A user with this username and password was not found.')
        user = authenticate(username=email, password=password)
        if  user is None:
            raise serializers.ValidationError(
                'A user with this email and password was not found.')
        if not user.is_active:
            raise serializers.ValidationError(
                'This user has been deactivated.')
        return {
            'email': user.email,
            'username': user.username,
            'token': user.token}