1.11: Value error on related user name during save of user model

While upgrading from 1.9 to 1.11, ForwardManyToOneDescriptor.__set__()
tries to assign a string (description of the related instance) to the related user name field
of user model.

class AbstractEmailUser(AbstractBaseUser, PermissionsMixin, FieldlistForDetailTemplateMixin):
localemail = models.OneToOneField('Mailbox', verbose_name=_('Local E-mail'),
related_name='localemail', db_column='localemail',
editable=('UR', 'UE', 'UL'))

objects = UserManager()

USERNAME_FIELD = 'localemail'
REQUIRED_FIELDS = []

class Meta:
abstract = True
ordering = ['localemail']

def get_username(self):
return getattr(self, self.USERNAME_FIELD)

class Mailbox(models.Model):
id = models.AutoField(primary_key=True)
localpart = models.CharField(_('Localpart'), max_length=40)
localdomainfk = models.ForeignKey(Localdomain, verbose_name=_('Domain'), db_column='localdomainfk', editable=('AL',))
…

def __str__(self):
return self.localpart+ '@'+self.localdomainfk.name


Internal Server Error: /admin/erdb/account/19/change/
Traceback (most recent call last):
File "...python3.5/site-packages/django/core/handlers/exception.py", line 41, in inner
response = get_response(request)
File "...python3.5/site-packages/django/core/handlers/base.py", line 249, in _legacy_get_response
response = self._get_response(request)
File "...python3.5/site-packages/django/core/handlers/base.py", line 187, in _get_response
response = self.process_exception_by_middleware(e, request)
File "...python3.5/site-packages/django/core/handlers/base.py", line 185, in _get_response
response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/contextlib.py", line 30, in inner
return func(*args, **kwds)
File "...python3.5/site-packages/django/contrib/admin/options.py", line 551, in wrapper
return self.admin_site.admin_view(view)(*args, **kwargs)
File "...python3.5/site-packages/django/utils/decorators.py", line 149, in _wrapped_view
response = view_func(request, *args, **kwargs)
File "...python3.5/site-packages/django/views/decorators/cache.py", line 57, in _wrapped_view_func
response = view_func(request, *args, **kwargs)
File "...python3.5/site-packages/django/contrib/admin/sites.py", line 224, in inner
return view(request, *args, **kwargs)
File "...python3.5/site-packages/django/contrib/admin/options.py", line 1511, in change_view
return self.changeform_view(request, object_id, form_url, extra_context)
File "...python3.5/site-packages/django/utils/decorators.py", line 67, in _wrapper
return bound_func(*args, **kwargs)
File "...python3.5/site-packages/django/utils/decorators.py", line 149, in _wrapped_view
response = view_func(request, *args, **kwargs)
File "...python3.5/site-packages/django/utils/decorators.py", line 63, in bound_func
return func.__get__(self, type(self))(*args2, **kwargs2)
File "...python3.5/site-packages/django/contrib/admin/options.py", line 1408, in changeform_view
return self._changeform_view(request, object_id, form_url, extra_context)
File "...python3.5/site-packages/django/contrib/admin/options.py", line 1440, in _changeform_view
if form.is_valid():
File "...python3.5/site-packages/django/forms/forms.py", line 183, in is_valid
return self.is_bound and not self.errors
File "...python3.5/site-packages/django/forms/forms.py", line 175, in errors
self.full_clean()
File "...python3.5/site-packages/django/forms/forms.py", line 386, in full_clean
self._post_clean()
File "...python3.5/site-packages/django/forms/models.py", line 408, in _post_clean
self.instance.full_clean(exclude=exclude, validate_unique=False)
File "...python3.5/site-packages/django/db/models/base.py", line 1234, in full_clean
self.clean()
File "...python3.5/site-packages/django/contrib/auth/base_user.py", line 77, in clean
setattr(self, self.USERNAME_FIELD, self.normalize_username(self.get_username()))
File "...python3.5/site-packages/django/db/models/fields/related_descriptors.py", line 216, in __set__
self.field.remote_field.model._meta.object_name,
ValueError: Cannot assign "'unpriv@framailx.de'": "Account.localemail" must be a "Mailbox" instance.
[21/Aug/2017 16:08:37] "POST /admin/erdb/account/19/change/ HTTP/1.1" 500 166385

Any help to resolve this appreciated,
Axel
---
PGP-Key:29E99DD6 ☀ computing @ chaos claudius

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