title: Could not import 'oauth2_provider.ext.rest_framework.OAuth2Authentication' for API setting 'DEFAULT_AUTHENTICATION_CLASSES'
body: <p>It's the first time I work with django rest and Django Oauth toolkit
  I'm following this tutorial 
  <a href="https://yeti.co/blog/oauth2-with-django-rest-framework/" rel="noreferrer">oauth2-with-django-rest-framework</a>
  But when I run python manage.py migrate I get the following error:</p>
  
  <p>ImportError: Could not import 'oauth2_provider.ext.rest_framework.OAuth2Authentication' for API setting 'DEFAULT_AUTHENTICATION_CLASSES'. ImportError: No module named ext.rest_framework.</p>
  
  <p>What is going wrong ? is there another module I should install ? 
  my virtual environment contains : </p>
  
  <p>certifi==2017.4.17</p>
  
  <p>chardet==3.0.4</p>
  
  <p>Django==1.11.2</p>
  
  <p>django-extensions==1.8.1</p>
  
  <p>django-oauth-toolkit==1.0.0</p>
  
  <p>djangorestframework==3.6.3</p>
  
  <p>idna==2.5</p>
  
  <p>oauthlib==2.0.2</p>
  
  <p>pytz==2017.2</p>
  
  <p>requests==2.18.1</p>
  
  <p>six==1.10.0</p>
  
  <p>Unidecode==0.4.21</p>
  
  <p>urllib3==1.21.1</p>