title: Django error with sites package: "The model Site is already registered in app 'sites'"
body: <p>I am trying to install the sites package and upon running makemigrations am receiving the error:</p>
  <blockquote>
  <p>django.contrib.admin.sites.AlreadyRegistered: The model Site is
  already registered in app 'sites'.</p>
  </blockquote>
  <p>This is my admin.py:</p>
  <pre><code>from django.contrib import admin
  
  # Register your models here.
  from django.apps import apps
  
  models = apps.get_models()
  
  for model in models:
      try:
          admin.site.register(model)
      except admin.sites.AlreadyRegistered:
          pass
  </code></pre>
  <p>And here are my installed apps:</p>
  <pre><code>INSTALLED_APPS = [
      'django.contrib.admin',
      'django.contrib.auth',
      'django.contrib.contenttypes',
      'django.contrib.sessions',
      'django.contrib.messages',
      'django.contrib.staticfiles',
      'webpage',
      'django_user_agents',
      'analytical',
      'corsheaders',
      'django.contrib.sites',
  ]
  </code></pre>
  <p>Any idea what might be causing this issue? Please let me know if there is information missing.</p>