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Why leads deletion of UUIDField to Django SystemCheckError

I've been building a Django website and included a UUID field "customer_id" in my initial "Customer" model. Finally, I decided to drop it. But when I try to delete it from my models.py, Django throws
SystemCheckError: System check identified some issues:
ERRORS:
<class 'accounts.admin.CustomerAdmin'>: (admin.E035) The value of 'readonly_fields[1]' is not a callable, an attribute of 'CustomerAdmin', or an attribute of 'accounts.Customer'.
Here is the code of models.py
from django.db import models
import uuid
# Create a base model to make sure we keep track of creation and edits
class ModelBaseClass(models.Model):
date_created = models.DateTimeField(auto_now_add=True, null=True)
date_modified = models.DateTimeField(auto_now=True, null=True)
class Meta:
abstract = True
# Create your models here.
class Customer(ModelBaseClass):
customer_id = models.UUIDField(default=uuid.uuid4, #this is the field i try to drop
editable=False,
unique=True)
name = models.CharField(max_length=200, null=True)
email = models.CharField(max_length=200, null=True)
def __str__(self):
return self.name
What I tried so far:
I suspect that this could be related to existing data or some other dependencies. So...
I deleted the sqlite database, deleted all migration files and ran
"python manage.py makemigrations" and "python manage.py migrate".
I ran python manage.py flush.
I also tried to change the editable=False to editable=True and migrate before dropping,
but it didn't change anything.
It's perhaps also worth mentioning that my "Customer" model a relation to another model.
Could someone explain me why Django is preventing me from deleting this field and how to resolve this?
Thanks! :)

Could someone explain me what's going on and how to resolve this?
As the error says, you have a model admin named CustomerAdmin. Indeed:
<class 'accounts.admin.CustomerAdmin'>: (admin.E035) The value of 'readonly_fields[1]' is not a callable, an attribute of 'CustomerAdmin', or an attribute of 'accounts.Customer'.
For the readonly_fields, it lists the customer_id, but since that field is no longer available, it raises the error.

Delete 2 model different objects which reference each other as foreign keys

We have two Django models:
class Project(models.Model):
project_title = models.CharField(max_length=30)
owner = models.ForeignKey(User, null=True, on_delete=models.DO_NOTHING)
class User(models.Model):
usernmae = models.CharField(max_length=50)
active_project = models.ForeignKey(User, null=True, on_delete=models.DO_NOTHING, related_name='current_project')
I have a user with object (with id say 692). And this user created a project with id=12345, therefore these owner field will get have this particular referenced.
I want to delete that user. But it shows error that
delete on table "app_user" violates foreign key constraint
This is expected as on_delete=models.DO_NOTHING, was set. One way I found out was using on_delete=models.CASCADE.
Question: How should I go about deleting the user (692) without changing the model definition(having to re-run migration)?
Doing it manually by deleting the project first, leads to the same foreign-key error, as owner field is User object.
How to handle this mutual foreign key relationship while deleting, as deleting any one of those two throws the foreign-key exception?
Update
Some correction in the model definition username is the field name instead of usernmae (typo). And the foreignkey for project is Project not the User model.
class Project(models.Model):
project_title = models.CharField(max_length=30)
owner = models.ForeignKey(User, null=True, on_delete=models.DO_NOTHING)
class User(models.Model):
username = models.CharField(max_length=50)
active_project = models.ForeignKey(Project, null=True, on_delete=models.DO_NOTHING, related_name='current_project')

IF you really don't want to make a migration (any specific reason?) and if you are ok with doing this manually this time. Then you have two options:
Go into the admin panel and manually change the User field in the project instance to a different user or to NULL. Now you should be able to delete the User instance since it's not referred anymore into the project.
If that worked, you can then delete the project instane as well.
Curios if this will work, let me know!

How to insert data into a relational one to one table in django?

I have a UserProfile table which is in relation with the default Django User table. Here's how it looks.
class UserProfile(models.Model):
user = user.OneToOneField(User, on_delete=models.CASCADE)
section = models.CharField(max_length=255, blank=True)
year = models.IntegerField(null=True, blank=True)
course = models.CharField(max_length=255, blank=True)
qrcode = models.CharField(max_length=255, blank=True)
present = models.BooleanField(default=False)
I am trying to insert the data into the UserProfile table using the Django Shell.
from users.models import UserProfile
a = UserProfile(qrcode="hello")
a.save()
This is how I have always known to insert data into tables, it has always worked. BUT when i try to do this in UserProfile model. I get this exception. NOT NULL constraint failed: users_userprofile.user_id. Which in turn is caused by the following exception Error in formatting: RelatedObjectDoesNotExist: UserProfile has no user.
I somewhat understand that I somehow need to supply a user instance. But I am clueless as to how. Can someone please help me.

Firstly you need to create User.
u1 = User(username='user1')
u1.save()
Create a UserProfile. Pass the ID of the “parent” object as this object’s ID:
v1 = UserProfile(user=u1, ....)
v1.save()
refer this

You need to create your User first
user = User.objects.create(username='user')
and then you can do:
user_profile = UserProfile.objects.create(user=user, ...)

What field Django used in FOO_set?

I am little bit comfused. Lets say I have such models.
models.py:
class Company(models.Model):
name = models.CharField(blank=False, null=False)
class Game(models.Model):
developer = models.ForeignKey(Company, on_delete=models.CASCADE)
publishers = models.ManyToManyField(Company)
If I use next code:
current_company = Company.object.get(pk=1)
current_company.game_set.all()
as I understand it return all games of current_company, but what field (developer or publishers) Django used?

But this code wouldn't be valid, for precisely this reason. If you tried to run it, Django would tell you that there was a conflict in the reverse relation.
If you have two relationships pointing to the same model, you need to explicitly set related_name on one of them to avoid this conflict.

Django error when removing ForeignKey relationship

I have a class as following:
class Mission(models.Model):
taxi = ForeignKey(Taxi, null=True, blank=True, unique=True, related_name="mission")
passenger = ForeignKey(Passenger, null=True, blank=True, unique=True, related_name="mission")
Now there's a method in the Class Taxi:
def turn_free(self):
....
self.mission_set.clear()
passenger.mission_set.clear() # passenger has been fetched
The first attempt to clear mission in Taxi proceed successfully, but the second one for the passenger reports an error: ccst_mission.passenger_id may not be NULL
Could someone help me?

Make sure your database has been updated properly.
For example, if you originally had (without specifying null=True)
passenger = Foreignkey(Passsenger, unique=True)
And added the null=True later on, a regular syncdb will not update that column to allow null.
If any of that sounds familiar, try doing an sqlclear on the app (or deleting the database entirely) then doing a fresh syncdb.