dynamic default value that uses the orm cause an exception when running migrate

[Brandon]

for example

def calc_number():
    a = A.objects.order_by("number").last()
    if a:
        return a.number+1
    return 1

class A(models.Model):
    number = models.IntegerField(default=calc_number)

when running migrate calc_number() is called as well and since that table doesn't exist yet in the db it raises a django.db.utils.ProgrammingError
I've tried to catch the exception inside calc_number but it raises another exception

django.db.utils.InternalError: current transaction is aborted, commands ignored until end of transaction block

the only workaround I've found is to use traceback to check if one of the function called is "migrate"

import traceback
for s in traceback.extract_stack():
    if s[2] == "migrate":
        return 1

[Tim Graham]

Duplicate of #24182