Nessuna modifica rilevata quando eseguo Python manage.py makemigrations ed eseguo la migrazione

il programma funziona rimuovendo abstract = True nella classe meta.dopo averlo rimosso quando eseguo python manage.py makemigrations tithe e python manage.py migrate tithe funziona bene

from __future__ import unicode_literals
from django.utils import timezone
from django.contrib.auth.models import User
from django.conf import settings
from django.contrib.auth import get_user_model
from django.core.signals import setting_changed
from django.dispatch import receiver
from django.db import models

# Create your models here.
class tithe(models.Model):
    member_code = models.ForeignKey(settings.AUTH_USER_MODEL)
    member = models.CharField(max_length=45)
    receipt_code = models.CharField(max_length=45, unique=True)
    tithes = models.IntegerField()
    combinedoffering = models.IntegerField()
    campmeetingoffering = models.IntegerField()
    churchbuilding = models.IntegerField()
    conference = models.IntegerField()
    localchurch = models.IntegerField()
    funds = models.IntegerField()
    total = models.IntegerField()
    created_date = models.DateTimeField(
            default=timezone.now)
    published_date = models.DateTimeField(
            blank=True, null=True)

    def publish(self):
        self.published_date = timezone.now()
        self.save()

    def __str__(self):
        return self.receitcode

    class Meta:
        unique_together = ["receipt_code"]