title: Specifying a namespace in include() without providing an app_name. Giving app_name also doesn't work
body: <pre><code>from django.conf import  settings
  from django.conf.urls.static import static
  
  from django.conf.urls import  url, include
  from django.contrib import  admin
  from django.views.generic import TemplateView
  
  
  from carts.views import cart_home
  
  from .views import  home_page, about_page, contact_page, login_page, register_page
  app_name = 'products'
  urlpatterns = [
      url(r'^$', home_page, name='home'),
      url(r'^about/$', about_page, name='about'),
      url(r'^contact/$', contact_page, name='contact'),
      url(r'^login/$', login_page,name='login'),
      #url(r'^cart/', include("carts.urls"),
      url(r'^register/$', register_page, name='register'),
      url(r'^bootstrap/$', TemplateView.as_view(template_name='bootstrap/example.html')),
      url(r'^products/', include("products.urls", namespace='products')),
  
      url(r'^admin/', admin.site.urls),
  ]
  </code></pre>
  
  <p>Please Help. I am getting this error : </p>
  
  <blockquote>
    <p>'Specifying a namespace in include() without providing an app_name '
    django.core.exceptions.ImproperlyConfigured: Specifying a namespace in
    include() without providing an app_name is not supported. Set the
    app_name attribute in the included module, or pass a 2-tuple
    containing the list of patterns and app_name instead.</p>
  </blockquote>
  
  <p><strong>products\urls.py:</strong></p>
  
  <pre><code>from django.conf.urls import url
  
      from .views import(
              ProductListView,
              ProductDetailSlugView,
          )
  
      urlpatterns = [
          url(r'^$', ProductListView.as_view(), name='list'),
          url(r'^(?P&lt;slug&gt;[\w-]+)/$', ProductDetailSlugView.as_view(), name='detail'),
      ]
  </code></pre>
  
  <p><strong>products\models.py:</strong></p>
  
  <pre><code>import random
  import os
  from django.db import models
  from django.db.models.signals import pre_save, post_save
  from django.urls import reverse
  
  from .utils import  unique_slug_generator
  
  def get_filename_ext(filepath):
      basename = os.path.basename(filepath)
      name, ext = os.path.splitetext(base_name)
      return name, ext
  
  def upload_image_path(instance, filename):
      # print(instance)
      # print(filename)
      new_filename = random.randint(1, 3910209312)
      name, ext = get_filename_ext(filename)
      final_filename = '{new_filename}{ext}',format(new_filename=new_filename, ext=ext)
      return "products/{new_filename)/{final_filename}",format(
          new_filename=new_filename,
          final_filename=final_filename
          )
  
  class ProductQuerySet(models.query.QuerySet):
      def active( self ):
          return self.filter(active = True)
      def featured( self ):
          return self.filter(featured = True, active = True)
  
  class ProductManager(models.Manager):
      def get_queryset( self ):
          return ProductQuerySet(self.model, using = self._db)
      def all( self ):
          return self.get_queryset().active()
      def featured( self ): #Product.objects.featured
          return self.get_queryset().featured()
  
      def get_by_id( self, id ):
          qs = self.get_queryset().filter(id = id)
          if qs.count() == 1:
              return qs.first()
          return None
  
  class Product(models.Model):
      title       = models.CharField(max_length=120)
      slug        = models.SlugField(blank=True, unique=True)
      description = models.TextField()
      price       = models.DecimalField(decimal_places=2, max_digits=20, default=39.99)
      image       = models.ImageField(upload_to=upload_image_path, null=True, blank=True)
      featured    = models.BooleanField(default=False)
      active      = models.BooleanField(default=True)
      timestamp   = models.DateTimeField(auto_now_add=True)
  
      objects = ProductManager()
  
      def __str__(self):
          return self.title
  
      def __unicode__(self):
          return self.title
      @property
      def name(self):
          return self.title
  
  def product_pre_save_receiver(sender, instance, *args, **kwargs):
      if not instance.slug:
          instance.slug = unique_slug_generator(instance)
  
  pre_save.connect(product_pre_save_receiver, sender=Product)
  </code></pre>