title: Django 'type' object is not iterable
body: <p>I made a simple API that list students their respected universities using Django Rest Framework. The url to list the data is <code>http://127.0.0.1:8000/api/v1/students/</code>. After trying out the API,I got the following error</p>
  
  <pre><code>TypeError at /api/v1/students/
  'type' object is not iterable
  
  Internal Server Error: /api/v1/students/
  Traceback (most recent call last):
    File "/Users/gilangramadhanilhami/Desktop/88sparses/shipment/tracking/lib/python3.6/site-packages/django/core/handlers/exception.py", line 35, in inner
      response = get_response(request)
    File "/Users/gilangramadhanilhami/Desktop/88sparses/shipment/tracking/lib/python3.6/site-packages/django/core/handlers/base.py", line 128, in _get_response
      response = self.process_exception_by_middleware(e, request)
    File "/Users/gilangramadhanilhami/Desktop/88sparses/shipment/tracking/lib/python3.6/site-packages/django/core/handlers/base.py", line 126, in _get_response
      response = wrapped_callback(request, *callback_args, **callback_kwargs)
    File "/Users/gilangramadhanilhami/Desktop/88sparses/shipment/tracking/lib/python3.6/site-packages/django/views/decorators/csrf.py", line 54, in wrapped_view
      return view_func(*args, **kwargs)
    File "/Users/gilangramadhanilhami/Desktop/88sparses/shipment/tracking/lib/python3.6/site-packages/django/views/generic/base.py", line 69, in view
      return self.dispatch(request, *args, **kwargs)
    File "/Users/gilangramadhanilhami/Desktop/88sparses/shipment/tracking/lib/python3.6/site-packages/rest_framework/views.py", line 477, in dispatch
      request = self.initialize_request(request, *args, **kwargs)
    File "/Users/gilangramadhanilhami/Desktop/88sparses/shipment/tracking/lib/python3.6/site-packages/rest_framework/views.py", line 379, in initialize_request
      authenticators=self.get_authenticators(),
    File "/Users/gilangramadhanilhami/Desktop/88sparses/shipment/tracking/lib/python3.6/site-packages/rest_framework/views.py", line 273, in get_authenticators
      return [auth() for auth in self.authentication_classes]
  TypeError: 'type' object is not iterable
  </code></pre>
  
  <p>I was able to find some solution on StackOverflow but not much luck in finding a solution. I am using <code>APIView</code> in the <code>views.py</code> file and I want to understand why this happens when I used <code>APIView</code> (this issue also appears using <code>Viewset</code>).</p>
  
  <p>I've tried changing the changing the permissions did not help. Also setting <code>many=True</code> to 'False' did not solve the issue also.</p>
  
  <p>Anybody has any ideas? Thanks in advance.</p>
  
  <p>Here is the other files for better understanding of this issue</p>
  
  <p><strong>models.py</strong></p>
  
  <pre><code>from django.db import models
  
  class University(models.Model):
      name = models.CharField(max_length=50)
      url = models.URLField(unique=True)
  
      class Meta:
          verbose_name = "University"
          verbose_name_plural = "Universities"
  
      def __str__(self):
          return self.name
  
  class Student(models.Model):
      first_name = models.CharField(max_length=50)
      last_name = models.CharField(max_length=50)
      university = models.ForeignKey(University, on_delete=models.CASCADE,)
  
      class Meta:
          verbose_name = "Student"
          verbose_name_plural = "Students"
  
  
      def __str__(self):
          return '%s %s' % (self.first_name, self.last_name)
  </code></pre>
  
  <p><strong>serializers.py</strong></p>
  
  <pre><code>from rest_framework import serializers
  
  from . import models
  
  class StudentSerializer(serializers.ModelSerializer):
      class Meta:
          fields = (
              'id',
              'first_name',
              'last_name',
              'university'
          )
          model = models.Student
  
  class UniversitySerializer(serializers.ModelSerializer):
      class Meta:
          fields = (
              'id',
              'name',
              'url'
          )
          model = models.University
  </code></pre>
  
  <p><strong>views.py</strong></p>
  
  <pre><code>from rest_framework.views import APIView
  from rest_framework.response import Response
  
  from . import models
  from . import serializers
  
  class ListStudent(APIView):
      def list(self, request, format=None):
          students = models.Student.objects.all()
          serializer = serializers.StudentSerializer(students, many=True)
          return Response(serializer.data)
  </code></pre>
  
  <p><strong>students/urls.py</strong></p>
  
  <pre><code>from django.urls import path
  
  from . import views
  
  urlpatterns = [
      path('', views.ListStudent.as_view(), name='student_list')
  ]
  </code></pre>
  
  <p><strong>urls.py</strong></p>
  
  <pre><code>from django.contrib import admin
  from django.urls import path, include
  
  urlpatterns = [
      path('admin/', admin.site.urls),
      path('api-auth/', include('rest_framework.urls', namespace='rest_framework')),
      path('api/v1/students/', include(('students.urls','students'), namespace='students')),
  ]
  </code></pre>