title: "Models aren't loaded yet" error while populating in Django 1.8 or later
body: <p>I am using this code to populate my database:</p>
  
  <pre><code>import os
  def populate():
      python_cat = add_cat('Python')
  
      add_page(cat=python_cat, 
      title="Official Python Tutorial",
      url="http://docs.python.org/2/tutorial/")
  
      add_page(cat=python_cat,
      title="How to Think like a Computer Scientist",
      url="http://www.greenteapress.com/thinkpython/")
  
      add_page(cat=python_cat,
      title="Learn Python in 10 minutes",
      url="http://www.korokithakis.net/tutorials/python/")
  
      django_cat = add_cat(name="Django")
  
      add_page(cat=django_cat,
      title="Official Django Tutorial",
      url="http://djangoproject.com/en/1.5/intro/tutorial01/")
  
      add_page(cat=django_cat,
      title="Django Rocks",
      url="http://www.djangorocks.com/")
  
      add_page(cat=django_cat,
      title="How to Tango with Django",
      url="htttp://www.tangowithdjango.com/")
  
      frame_cat = add_cat(name="Other Frameworks")
  
      add_page(cat=frame_cat, 
      title="Bottle",
      url="http://bottlepy.org/docs/dev/")
  
      add_page(cat=frame_cat, 
      title="Flask",
      url="http://flask.pocoo.org")
  
      # Print out what we have added to the user. 
      for c in Category.objects.all():
          for p in Page.objects.filter(category=c):
              print "- {0} - {1}".format(str(c), str(p))
  
  def add_page(cat, title, url, views=0):
      p = Page.objects.get_or_create(category=cat, title=title, url=url, views=views)[0]
      return p
  
  def add_cat(name):
      c = Category.objects.get_or_create(name=name)
      return c
  
  if __name__ == '__main__':
      print "Starting Rango population script..."
      os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'p.settings')
      from rango.models import Category, Page
      populate()
  </code></pre>
  
  <p>On running</p>
  
  <pre><code>python c:\python27\p\populate_rango.py
  </code></pre>
  
  <p>It gives the error:</p>
  
  <pre><code>Staring Rango population script...
  Traceback (most recent call last):
  File "c:\python27\p\populate_rango.py", line 59, in &lt;module&gt;
  populate()
  File "c:\python27\p\populate_rango.py", line 4, in populate
  python_cat = add_cat('Python')
  File "c:\python27\p\populate_rango.py", line 52, in add_cat
  c = Category.objects.get_or_create(name=name)
  File "C:\Python27\Lib\site-packages\django\db\models\manager.py", li
  manager_method
  return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "C:\Python27\Lib\site-packages\django\db\models\query.py", line
  et_or_create
  return self.get(**lookup), False
  File "C:\Python27\Lib\site-packages\django\db\models\query.py", line
  clone = self.filter(*args, **kwargs)
  File "C:\Python27\Lib\site-packages\django\db\models\query.py", line
  ilter
  return self._filter_or_exclude(False, *args, **kwargs)
  File "C:\Python27\Lib\site-packages\django\db\models\query.py", line
  filter_or_exclude
  clone.query.add_q(Q(*args, **kwargs))
  File "C:\Python27\Lib\site-packages\django\db\models\sql\query.py",
  in add_q
  clause, require_inner = self._add_q(where_part, self.used_aliases)
  File "C:\Python27\Lib\site-packages\django\db\models\sql\query.py",
  in _add_q
  current_negated=current_negated, connector=connector)
  File "C:\Python27\Lib\site-packages\django\db\models\sql\query.py",
  in build_filter
  lookups, parts, reffed_aggregate = self.solve_lookup_type(arg)
  File "C:\Python27\Lib\site-packages\django\db\models\sql\query.py",
  in solve_lookup_type
  _, field, _, lookup_parts = self.names_to_path(lookup_splitted, se
  a())
  File "C:\Python27\Lib\site-packages\django\db\models\sql\query.py",
  in names_to_path
  field, model, direct, m2m = opts.get_field_by_name(name)
  File "C:\Python27\Lib\site-packages\django\db\models\options.py", li
  get_field_by_name
  cache = self.init_name_map()
  File "C:\Python27\Lib\site-packages\django\db\models\options.py", li
  init_name_map
  for f, model in self.get_all_related_m2m_objects_with_model():
  File "C:\Python27\Lib\site-packages\django\db\models\options.py", li
  get_all_related_m2m_objects_with_model
  cache = self._fill_related_many_to_many_cache()
  File "C:\Python27\Lib\site-packages\django\db\models\options.py", li
  _fill_related_many_to_many_cache
  for klass in self.apps.get_models():
  File "C:\Python27\Lib\site-packages\django\utils\lru_cache.py", line
  rapper
  result = user_function(*args, **kwds)
  File "C:\Python27\Lib\site-packages\django\apps\registry.py", line 1
  _models
  *self.check_models_ready()
  File "C:\Python27\Lib\site-packages\django\apps\registry.py", line 1
  ck_models_ready
  raise AppRegistryNotReady("Models aren't loaded yet.")
  django.core.exceptions.AppRegistryNotReady: Models aren't loaded yet.*
  </code></pre>
  
  <p>Rest of my files are ok but getting this error. I am following the tutorial from <em>Tango with Django</em> book but as the book refers to Django 1.5.4 and i am using Django 1.8, so can anyone help me here?</p>