title: Django viewset has not attribute 'get_extra_actions'
body: <p>I am working with Django for a first time and I'm trying to build an API and I am following some tutorials and examples and it works right, but I am running the project now in a Raspberry Pi after install all the requirements and the project is failing with the following error:</p>
  
  <pre><code>    Performing system checks...
  
  Unhandled exception in thread started by &lt;function check_errors.&lt;locals&gt;.wrapper at 0xb547adb0&gt;
  Traceback (most recent call last):
    File "/home/pi/.local/lib/python3.5/site-packages/django/utils/autoreload.py", line 225, in wrapper
      fn(*args, **kwargs)
    File "/home/pi/.local/lib/python3.5/site-packages/django/core/management/commands/runserver.py", line 120, in inner_run
      self.check(display_num_errors=True)
    File "/home/pi/.local/lib/python3.5/site-packages/django/core/management/base.py", line 364, in check
      include_deployment_checks=include_deployment_checks,
    File "/home/pi/.local/lib/python3.5/site-packages/django/core/management/base.py", line 351, in _run_checks
      return checks.run_checks(**kwargs)
    File "/home/pi/.local/lib/python3.5/site-packages/django/core/checks/registry.py", line 73, in run_checks
      new_errors = check(app_configs=app_configs)
    File "/home/pi/.local/lib/python3.5/site-packages/django/core/checks/urls.py", line 13, in check_url_config
      return check_resolver(resolver)
    File "/home/pi/.local/lib/python3.5/site-packages/django/core/checks/urls.py", line 23, in check_resolver
      return check_method()
    File "/home/pi/.local/lib/python3.5/site-packages/django/urls/resolvers.py", line 397, in check
      for pattern in self.url_patterns:
    File "/home/pi/.local/lib/python3.5/site-packages/django/utils/functional.py", line 36, in __get__
      res = instance.__dict__[self.name] = self.func(instance)
    File "/home/pi/.local/lib/python3.5/site-packages/django/urls/resolvers.py", line 536, in url_patterns
      patterns = getattr(self.urlconf_module, "urlpatterns", self.urlconf_module)
    File "/home/pi/.local/lib/python3.5/site-packages/django/utils/functional.py", line 36, in __get__
      res = instance.__dict__[self.name] = self.func(instance)
    File "/home/pi/.local/lib/python3.5/site-packages/django/urls/resolvers.py", line 529, in urlconf_module
      return import_module(self.urlconf_name)
    File "/usr/lib/python3.5/importlib/__init__.py", line 126, in import_module
      return _bootstrap._gcd_import(name[level:], package, level)
    File "&lt;frozen importlib._bootstrap&gt;", line 986, in _gcd_import
    File "&lt;frozen importlib._bootstrap&gt;", line 969, in _find_and_load
    File "&lt;frozen importlib._bootstrap&gt;", line 958, in _find_and_load_unlocked
    File "&lt;frozen importlib._bootstrap&gt;", line 673, in _load_unlocked
    File "&lt;frozen importlib._bootstrap_external&gt;", line 673, in exec_module
    File "&lt;frozen importlib._bootstrap&gt;", line 222, in _call_with_frames_removed
    File "/home/pi/Projects/openvpn-monitor/openvpnmonitor/urls.py", line 24, in &lt;module&gt;
      url(r'^api/', include('openvpnmonitor.api.urls')),
    File "/home/pi/.local/lib/python3.5/site-packages/django/urls/conf.py", line 34, in include
      urlconf_module = import_module(urlconf_module)
    File "/usr/lib/python3.5/importlib/__init__.py", line 126, in import_module
      return _bootstrap._gcd_import(name[level:], package, level)
    File "&lt;frozen importlib._bootstrap&gt;", line 986, in _gcd_import
    File "&lt;frozen importlib._bootstrap&gt;", line 969, in _find_and_load
    File "&lt;frozen importlib._bootstrap&gt;", line 958, in _find_and_load_unlocked
    File "&lt;frozen importlib._bootstrap&gt;", line 673, in _load_unlocked
    File "&lt;frozen importlib._bootstrap_external&gt;", line 673, in exec_module
    File "&lt;frozen importlib._bootstrap&gt;", line 222, in _call_with_frames_removed
    File "/home/pi/Projects/openvpn-monitor/openvpnmonitor/api/urls.py", line 16, in &lt;module&gt;
      urlpatterns += router.urls
    File "/home/pi/.local/lib/python3.5/site-packages/rest_framework/routers.py", line 101, in urls
      self._urls = self.get_urls()
    File "/home/pi/.local/lib/python3.5/site-packages/rest_framework/routers.py", line 363, in get_urls
      urls = super(DefaultRouter, self).get_urls()
    File "/home/pi/.local/lib/python3.5/site-packages/rest_framework/routers.py", line 261, in get_urls
      routes = self.get_routes(viewset)
    File "/home/pi/.local/lib/python3.5/site-packages/rest_framework/routers.py", line 176, in get_routes
      extra_actions = viewset.get_extra_actions()
  AttributeError: type object 'SessionViewSet' has no attribute 'get_extra_actions'
  </code></pre>
  
  <p>My views.py has the following code:</p>
  
  <pre><code>from django.shortcuts import render
  
  from rest_framework import viewsets
  from .models import Session
  from .serializers import SessionSerializer
  
  from rest_framework.views import APIView, Response
  
  
  class SessionViewSet(APIView):
      queryset = Session.objects.all()
      serializer_class = SessionSerializer
  
      def get(self, request, format=None):
          return Response("test")
  </code></pre>
  
  <p>I really don't know why is working on my laptop but it is not working on my Raspberry Pi.</p>
  
  <p>Has this happened to someone or anyone knows why is happening this?</p>
  
  <p>Thank you so much!</p>
  
  <p>Edit:</p>
  
  <p>Here is my urls.py</p>
  
  <pre><code>from django.conf.urls import url
  from rest_framework import routers
  from openvpnmonitor.api.views import SessionViewSet
  
  router = routers.DefaultRouter()
  router.register(r'sessions', SessionViewSet)
  
  urlpatterns = [
      url(r'sessions', SessionViewSet.as_view()),
      url(r'^docs/', schema_view),
  ]
  
  urlpatterns += router.urls
  </code></pre>