ошибка при миграции базы данных при создании сайта Django

Question

**** Я использую Python v3.7 для создания веб-сайта с использованием Django Framework.
Я мог бы хорошо запустить веб-сервер. Но когда я попытался выполнить миграцию базы данных, запустив эту команду: python3 manage.py makemigrations, возникает ошибка: ****

Traceback (most recent call last):
  File "manage.py", line 22, in <module>
    execute_from_command_line(sys.argv)
  File "C:\Users\yangyj\AppData\Local\Continuum\anaconda3\lib\site-packages\djan
go\core\management\__init__.py", line 371, in execute_from_command_line
    utility.execute()
  File "C:\Users\yangyj\AppData\Local\Continuum\anaconda3\lib\site-packages\djan
go\core\management\__init__.py", line 365, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "C:\Users\yangyj\AppData\Local\Continuum\anaconda3\lib\site-packages\djan
go\core\management\base.py", line 288, in run_from_argv
    self.execute(*args, **cmd_options)
  File "C:\Users\yangyj\AppData\Local\Continuum\anaconda3\lib\site-packages\djan
go\core\management\base.py", line 335, in execute
    output = self.handle(*args, **options)
  File "C:\Users\yangyj\AppData\Local\Continuum\anaconda3\lib\site-packages\djan
go\core\management\commands\makemigrations.py", line 132, in handle
    loader.project_state(),
  File "C:\Users\yangyj\AppData\Local\Continuum\anaconda3\lib\site-packages\djan
go\db\migrations\loader.py", line 316, in project_state
    return self.graph.make_state(nodes=nodes, at_end=at_end, real_apps=list(self
.unmigrated_apps))
  File "C:\Users\yangyj\AppData\Local\Continuum\anaconda3\lib\site-packages\djan
go\db\migrations\graph.py", line 376, in make_state
    project_state = self.nodes[node].mutate_state(project_state, preserve=False)

  File "C:\Users\yangyj\AppData\Local\Continuum\anaconda3\lib\site-packages\djan
go\db\migrations\migration.py", line 85, in mutate_state
    operation.state_forwards(self.app_label, new_state)
  File "C:\Users\yangyj\AppData\Local\Continuum\anaconda3\lib\site-packages\djan
go\db\migrations\operations\fields.py", line 144, in state_forwards
    delay = not old_field.is_relation
AttributeError: 'NoneType' object has no attribute 'is_relation'

Код models.py:

from __future__ import unicode_literals
from django.db import models



from django.urls import reverse #Used to generate urls by reversing the URL patterns

from django.utils.html import format_html

from django.urls import reverse
from django.conf.urls import url
from .forms import *
from django.http import HttpResponseRedirect
from django.template.response import TemplateResponse
from getsqlite import *  

from django.db import models
from django.contrib import admin
from django.contrib.auth.models import User

class FW(models.Model):

    ODM_name = models.CharField(max_length=20)
    project_name = models.CharField(max_length=20)
    NAP = models.CharField(max_length=4)
    UAP = models.CharField(max_length=2)
    LAP = models.CharField(max_length=6)
    num_address = models.CharField(max_length=4)
    download = models.CharField(max_length=1000, blank=True)
    #level = models.CharField(max_length=10)
    #sg_sz = models.CharField(max_length=10)
    approve_time = models.DateField(null=True, blank=True)
    applier = models.ForeignKey(User, on_delete=models.SET_NULL, null=True, blank=True)


    APPROVE_STATUS = (
        ('a', 'approved'),
        ('d', 'disapproved'),

    )

    status = models.CharField(max_length=1, choices=APPROVE_STATUS, blank=True, default='d', help_text='FW APPROVE_STATUS')

    @property
    def is_approved(self):
        if self.status == 'a':

            return True
        return False

    class Meta:
        ordering = ["approve_time"]
        permissions = (("can_mark_used", "Set FW as used"),)

    def __str__(self):
        """
        String for representing the Model object.
        """
        #return '%s (%s)' % (self.id,self.FW.title)
        return '{0} ({1})'.format(self.id,self.FW.title)

    def display_project(self):
        """
        Creates a string for the project. This is required to display project in Admin.
        """
        return ', '.join([ project.name for project in self.project.all()[:3] ])
        display_project.short_description = 'project'


    def get_absolute_url(self):
        """
        Returns the url to access a particular FW instance.
        """
        return reverse('FW-detail', args=[str(self.id)])

    def __str__(self):
        """
        String for representing the Model object.
        """
        return self.project_name

    def call_exe(self):
        try:
            when_call_exe()
        except:
            return None

#class UserAdmin(admin.ModelAdmin):
    #list_display = ('ODM_name', 'project_name', 'NAP', 'UAP', 'LAP', 'num_address')




#admin.site.register(FW, UserAdmin)

import uuid # Required for unique FW instances
from datetime import date

from django.db import models
from django.contrib import admin


class FW_INSTANCE(models.Model):
    ODM_name = models.CharField(max_length=20)
    project_name = models.CharField(max_length=20)
    NAP = models.CharField(max_length=4)
    UAP = models.CharField(max_length=2)
    LAP = models.CharField(max_length=6)
    level = models.CharField(max_length=10)
    sg_sz = models.CharField(max_length=10)

Как я могу справиться с этой проблемой？ Когда я использую свой предыдущий, он может работать хорошо. Но после смены нового компьютера возникает эта ошибка.