old_contents: # -*- coding: utf-8 -*-
  from django.contrib.auth.models import User
  from django.db import models
  from django.utils.translation import ugettext_lazy as _
  from django.conf import settings
  from cms.utils.compat.dj import force_unicode, python_2_unicode_compatible
  
  
  @python_2_unicode_compatible
  class UserSettings(models.Model):
      user = models.ForeignKey(User, editable=False)
      language = models.CharField(_("Language"), max_length=10, choices=settings.LANGUAGES,
                                  help_text=_("The language for the admin interface and toolbar"))
      clipboard = models.ForeignKey('cms.Placeholder', blank=True, null=True, editable=False)
  
      class Meta:
          verbose_name = _('user setting')
          verbose_name_plural = _('user settings')
          app_label = 'cms'
  
      def __str__(self):
          return force_unicode(self.user)
  
  
  
new_contents: # -*- coding: utf-8 -*-
  from django.contrib.auth.models import User
  from django.db import models
  from django.utils.translation import ugettext_lazy as _
  from django.conf import settings
  from cms.utils.compat.dj import force_unicode, python_2_unicode_compatible
  
  
  @python_2_unicode_compatible
  class UserSettings(models.Model):
      user = models.ForeignKey(User, editable=False, related_name='djangocms_usersettings')
      language = models.CharField(_("Language"), max_length=10, choices=settings.LANGUAGES,
                                  help_text=_("The language for the admin interface and toolbar"))
      clipboard = models.ForeignKey('cms.Placeholder', blank=True, null=True, editable=False)
  
      class Meta:
          verbose_name = _('user setting')
          verbose_name_plural = _('user settings')
          app_label = 'cms'
  
      def __str__(self):
          return force_unicode(self.user)
  
  
  
subject: Define a custom related_name in UserSettings->User relation