问如何解决Django中的错误'IntegrityError at /admin/auth/user/add/ UNIQUE constraint failed: user_details_profile.phone‘？

EN

from django.db import models
from django.db.models.signals import post_save
from django.contrib.auth.models import User
from django.dispatch import receiver
from django.core.exceptions import ObjectDoesNotExist
from general.models import Ward

# Create your models here.
class Profile(models.Model):
    user = models.OneToOneField(User, on_delete=models.CASCADE)
    firstname = models.CharField(max_length=20)
    middlename = models.CharField(max_length=20)
    lastname = models.CharField(max_length=20)
    loc_id = models.CharField(max_length=8, unique=True)
    ward = models.ForeignKey(Ward, related_name="wards", null=True, on_delete=models.SET_NULL)
    phone = models.CharField(max_length=10, unique=True)
    address = models.CharField(max_length=255)
    postal_code = models.CharField(max_length=15)

    def __str__(self):
        return "{} {}".format(self.user.first_name, self.user.last_name)

    class Meta:
        verbose_name_plural = "Personal information"

@receiver(post_save, sender=User)
def create_user_profile(sender, instance, created, **kwargs):
    try:
        instance.profile.save()
    except ObjectDoesNotExist:
        Profile.objects.create(user=instance)

@receiver(post_save, sender=User)
def save_user_profile(sender, instance, **kwargs):
    try:
        instance.profile.save()
    except ObjectDoesNotExist:
        Profile.objects.create(user=instance)

Environment:
Request Method: POST
Request URL: http://localhost:8000/admin/auth/user/add/

Django Version: 2.1.1
Python Version: 3.6.0
Installed Applications:
['django.contrib.admin',
 'django.contrib.auth',
 'django.contrib.contenttypes',
 'django.contrib.sessions',
 'django.contrib.messages',
 'django.contrib.staticfiles',
 'rest_framework',
 'general',
 'user_details']
Installed Middleware:
['django.middleware.security.SecurityMiddleware',
 'django.contrib.sessions.middleware.SessionMiddleware',
 'django.middleware.common.CommonMiddleware',
 'django.middleware.csrf.CsrfViewMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware',
 'django.contrib.messages.middleware.MessageMiddleware',
 'django.middleware.clickjacking.XFrameOptionsMiddleware']



Traceback:

File "C:\xampp\htdocs\python\projects\tanariver\user_details\models.py" in create_user_profile
  30.         instance.profile.save()

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\db\models\fields\related_descriptors.py" in __get__
  414.                     self.related.get_accessor_name()

During handling of the above exception (User has no profile.), another exception occurred:

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\db\backends\utils.py" in _execute
  85.                 return self.cursor.execute(sql, params)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\db\backends\sqlite3\base.py" in execute
  296.         return Database.Cursor.execute(self, query, params)

The above exception (UNIQUE constraint failed: user_details_profile.phone) was the direct cause of the following exception:

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\core\handlers\exception.py" in inner
  34.             response = get_response(request)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\core\handlers\base.py" in _get_response
  126.                 response = self.process_exception_by_middleware(e, request)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\core\handlers\base.py" in _get_response
  124.                 response = wrapped_callback(request, *callback_args, **callback_kwargs)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\contrib\admin\options.py" in wrapper
  604.                 return self.admin_site.admin_view(view)(*args, **kwargs)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\utils\decorators.py" in _wrapped_view
  142.                     response = view_func(request, *args, **kwargs)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\views\decorators\cache.py" in _wrapped_view_func
  44.         response = view_func(request, *args, **kwargs)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\contrib\admin\sites.py" in inner
  223.             return view(request, *args, **kwargs)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\utils\decorators.py" in _wrapper
  45.         return bound_method(*args, **kwargs)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\views\decorators\debug.py" in sensitive_post_parameters_wrapper
  76.             return view(request, *args, **kwargs)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\utils\decorators.py" in _wrapper
  45.         return bound_method(*args, **kwargs)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\utils\decorators.py" in _wrapped_view
  142.                     response = view_func(request, *args, **kwargs)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\contrib\auth\admin.py" in add_view
  98.             return self._add_view(request, form_url, extra_context)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\contrib\auth\admin.py" in _add_view
  125.         return super().add_view(request, form_url, extra_context)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\contrib\admin\options.py" in add_view
  1636.         return self.changeform_view(request, None, form_url, extra_context)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\utils\decorators.py" in _wrapper
  45.         return bound_method(*args, **kwargs)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\utils\decorators.py" in _wrapped_view
  142.                     response = view_func(request, *args, **kwargs)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\contrib\admin\options.py" in changeform_view
  1525.             return self._changeform_view(request, object_id, form_url, extra_context)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\contrib\admin\options.py" in _changeform_view
  1564.                 self.save_model(request, new_object, form, not add)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\contrib\admin\options.py" in save_model
  1091.         obj.save()

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\contrib\auth\base_user.py" in save
  73.         super().save(*args, **kwargs)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\db\models\base.py" in save
  718.                        force_update=force_update, update_fields=update_fields)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\db\models\base.py" in save_base
  758.                 update_fields=update_fields, raw=raw, using=using,

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\dispatch\dispatcher.py" in send
  175.             for receiver in self._live_receivers(sender)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\dispatch\dispatcher.py" in <listcomp>
  175.             for receiver in self._live_receivers(sender)

File "C:\xampp\htdocs\python\projects\tanariver\user_details\models.py" in create_user_profile
  32.         Profile.objects.create(user=instance)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\db\models\manager.py" in manager_method
  82.                 return getattr(self.get_queryset(), name)(*args, **kwargs)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\db\models\query.py" in create
  413.         obj.save(force_insert=True, using=self.db)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\db\models\base.py" in save
  718.                        force_update=force_update, update_fields=update_fields)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\db\models\base.py" in save_base
  748.             updated = self._save_table(raw, cls, force_insert, force_update, using, update_fields)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\db\models\base.py" in _save_table
  831.             result = self._do_insert(cls._base_manager, using, fields, update_pk, raw)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\db\models\base.py" in _do_insert
  869.                                using=using, raw=raw)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\db\models\manager.py" in manager_method
  82.                 return getattr(self.get_queryset(), name)(*args, **kwargs)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\db\models\query.py" in _insert
  1136.         return query.get_compiler(using=using).execute_sql(return_id)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\db\models\sql\compiler.py" in execute_sql
  1289.                 cursor.execute(sql, params)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\db\backends\utils.py" in execute
  100.             return super().execute(sql, params)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\db\backends\utils.py" in execute
  68.         return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\db\backends\utils.py" in _execute_with_wrappers
  77.         return executor(sql, params, many, context)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\db\backends\utils.py" in _execute
  85.                 return self.cursor.execute(sql, params)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\db\utils.py" in __exit__
  89.                 raise dj_exc_value.with_traceback(traceback) from exc_value

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\db\backends\utils.py" in _execute
  85.                 return self.cursor.execute(sql, params)

File "C:\xampp\htdocs\python\envs\tanariver\lib\site-packages\django\db\backends\sqlite3\base.py" in execute
  296.         return Database.Cursor.execute(self, query, params)

Exception Type: IntegrityError at /admin/auth/user/add/
Exception Value: UNIQUE constraint failed: user_details_profile.phone