              name='Permission',
              fields=[
                  ('id', models.AutoField(verbose_name='ID', serialize=False, auto_created=True, primary_key=True)),
                  ('name', models.CharField(max_length=50, verbose_name='name')),
                  ('content_type', models.ForeignKey(to='contenttypes.ContentType', to_field='id', verbose_name='content type')),
                  ('codename', models.CharField(max_length=100, verbose_name='codename')),
              ],
              options={
                  'ordering': ('content_type__app_label', 'content_type__model', 'codename'),
                  'unique_together': set([('content_type', 'codename')]),
 
</s> remove             ('neighborhood', models.ForeignKey(to='gis_migrations.Neighborhood', to_field='id', null=True)),
 </s> add             ('neighborhood', models.ForeignKey(
                'gis_migrations.Neighborhood',
                models.SET_NULL,
                to_field='id',
                null=True,
            )), </s> remove                 ('content_type', models.ForeignKey(to_field='id', blank=True, to='contenttypes.ContentType', null=True, verbose_name='content type')),
                ('user', models.ForeignKey(to=settings.AUTH_USER_MODEL, verbose_name='user')),
 </s> add                 ('content_type', models.ForeignKey(
                    to_field='id',
                    on_delete=models.SET_NULL,
                    blank=True, null=True,
                    to='contenttypes.ContentType',
                    verbose_name='content type',
                )),
                ('user', models.ForeignKey(
                    to=settings.AUTH_USER_MODEL,
                    on_delete=models.CASCADE,
                    verbose_name='user',
                )), </s> remove                 ('author', models.ForeignKey('author_app.Author')),
 </s> add                 ('author', models.ForeignKey('author_app.Author', models.CASCADE)), </s> remove                 ('a1', models.ForeignKey(to='lookuperror_a.A1')),
 </s> add                 ('a1', models.ForeignKey('lookuperror_a.A1', models.CASCADE)), </s> remove                 ('b2', models.ForeignKey(to='lookuperror_b.B2')),
                ('c2', models.ForeignKey(to='lookuperror_c.C2')),
 </s> add                 ('b2', models.ForeignKey('lookuperror_b.B2', models.CASCADE)),
                ('c2', models.ForeignKey('lookuperror_c.C2', models.CASCADE)),
                ('content_type', models.ForeignKey(
                    to='contenttypes.ContentType',
                    on_delete=models.CASCADE,
                    to_field='id',
                    verbose_name='content type',
                )),
              name='Permission',
              fields=[
                  ('id', models.AutoField(verbose_name='ID', serialize=False, auto_created=True, primary_key=True)),
                  ('name', models.CharField(max_length=50, verbose_name='name')),
                ('content_type', models.ForeignKey(
                    to='contenttypes.ContentType',
                    on_delete=models.CASCADE,
                    to_field='id',
                    verbose_name='content type',
                )),
                  ('codename', models.CharField(max_length=100, verbose_name='codename')),
              ],
              options={
                  'ordering': ('content_type__app_label', 'content_type__model', 'codename'),
                  'unique_together': set([('content_type', 'codename')]),
keep keep keep keep replace keep keep keep keep keep
 Fixed #21127 -- Started deprecation toward requiring on_delete for ForeignKey/OneToOneField 
django/contrib/auth/migrations/0001_initial.py