AttributeError: 'RegexURLPattern' object has no attribute '_callback'
<p>I'm newbie in python. I used this tutorial <a href="http://www.django-rest-framework.org/tutorial/quickstart/" rel="noreferrer">http://www.django-rest-framework.org/tutorial/quickstart/</a>, but have an issue with <strong>RegexURLPattern</strong>. 
Full stack trace of issue:</p>

<pre><code> Unhandled exception in thread started by &lt;function check_errors.  
 &lt;locals&gt;.wrapper at 0x103c8cf28&gt;
 Traceback (most recent call last):
 File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/Django-1.10.dev20151224130822-py3.5.egg/django/utils/autoreload.py", line 226, in wrapper
 fn(*args, **kwargs)
 File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/Django-1.10.dev20151224130822-py3.5.egg/django/core/management/commands/runserver.py", line 116, in inner_run
 self.check(display_num_errors=True)
 File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/Django-1.10.dev20151224130822-py3.5.egg/django/core/management/base.py", line 366, in check
 include_deployment_checks=include_deployment_checks,
 File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/Django-1.10.dev20151224130822-py3.5.egg/django/core/checks/registry.py", line 75, in run_checks
 new_errors = check(app_configs=app_configs)
 File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/Django-1.10.dev20151224130822-py3.5.egg/django/core/checks/urls.py", line 10, in check_url_config
 return check_resolver(resolver)
 File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/Django-1.10.dev20151224130822-py3.5.egg/django/core/checks/urls.py", line 19, in check_resolver
 for pattern in resolver.url_patterns:
 File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/Django-1.10.dev20151224130822-py3.5.egg/django/utils/functional.py", line 35, in __get__
 res = instance.__dict__[self.name] = self.func(instance)
 File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/Django-1.10.dev20151224130822-py3.5.egg/django/core/urlresolvers.py", line 379, in url_patterns
 patterns = getattr(self.urlconf_module, "urlpatterns", self.urlconf_module)
 File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/Django-1.10.dev20151224130822-py3.5.egg/django/utils/functional.py", line 35, in __get__
 res = instance.__dict__[self.name] = self.func(instance)
 File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/Django-1.10.dev20151224130822-py3.5.egg/django/core/urlresolvers.py", line 372, in urlconf_module
 return import_module(self.urlconf_name)
 File "/Library/Frameworks/Python.framework/Versions/3.5/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 662, in exec_module
 File "&lt;frozen importlib._bootstrap&gt;", line 222, in _call_with_frames_removed
 File "/Users/igor/tutorial/tutorial/tutorial/urls.py", line 28, in &lt;module&gt;
 url(r'^', include(router.urls)),
 File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/rest_framework/routers.py", line 79, in urls
 self._urls = self.get_urls()
 File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/rest_framework/routers.py", line 321, in get_urls
 urls = format_suffix_patterns(urls)
 File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/rest_framework/urlpatterns.py", line 64, in format_suffix_patterns
 return apply_suffix_patterns(urlpatterns, suffix_pattern, suffix_required)
 File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/rest_framework/urlpatterns.py", line 27, in apply_suffix_patterns
 view = urlpattern._callback or urlpattern._callback_str
 AttributeError: 'RegexURLPattern' object has no attribute '_callback'
</code></pre>

<p>My urls.py content:</p>

<pre><code>from django.conf.urls import url, include
from rest_framework import routers
from quickstart import views

router = routers.DefaultRouter()
router.register(r'users', views.UserViewSet)
router.register(r'groups', views.GroupViewSet)

urlpatterns = [
       url(r'^', include(router.urls)),
       url(r'^api-auth/', include('rest_framework.urls', namespace='rest_framework'))
]
</code></pre>

<p>What i'am doing wrong? Help please...</p>