Fixed Django 2.1 compatibility due to removal of django.contrib.auth.login()/logout() views.

[felixxm]

Fixed Django 2.1 compatibility due to removal of django.contrib.auth.login()/logout() views (see Django documentation 1.11, 2.1).

________________ ERROR collecting tests/test_authentication.py _________________
tests/test_authentication.py:85: in <module>
    url(r'^auth/', include('rest_framework.urls', namespace='rest_framework')),
.tox/py35-djangomaster/lib/python3.5/site-packages/django/urls/conf.py:34: in include
    urlconf_module = import_module(urlconf_module)
.tox/py35-djangomaster/lib/python3.5/importlib/__init__.py:126: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
rest_framework/urls.py:24: in <module>
    url(r'^login/$', views.login, template_name, name='login'),
E   AttributeError: module 'django.contrib.auth.views' has no attribute 'login'

___________________ ERROR collecting tests/test_renderers.py ___________________
tests/test_renderers.py:121: in <module>
    url(r'^api', include('rest_framework.urls', namespace='rest_framework'))
.tox/py35-djangomaster/lib/python3.5/site-packages/django/urls/conf.py:34: in include
    urlconf_module = import_module(urlconf_module)
.tox/py35-djangomaster/lib/python3.5/importlib/__init__.py:126: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
rest_framework/urls.py:24: in <module>
    url(r'^login/$', views.login, template_name, name='login'),
E   AttributeError: module 'django.contrib.auth.views' has no attribute 'login'

___________________ ERROR collecting tests/test_response.py ____________________
tests/test_response.py:131: in <module>
    url(r'^restframework', include('rest_framework.urls', namespace='rest_framework'))
.tox/py35-djangomaster/lib/python3.5/site-packages/django/urls/conf.py:34: in include
    urlconf_module = import_module(urlconf_module)
.tox/py35-djangomaster/lib/python3.5/importlib/__init__.py:126: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
rest_framework/urls.py:24: in <module>
    url(r'^login/$', views.login, template_name, name='login'),
E   AttributeError: module 'django.contrib.auth.views' has no attribute 'login'

[carltongibson]

@felixxm Awesome! I was going to look into that. Thanks! (Will review fully in daylight)

[auvipy]

looks good

[rpkilby]

Off hand thought - defer this to December when Django 1.10 is deprecated. That way, the compat check isn't necessary.

[xordoquy]

As was said earlier, we shouldn't drop a django version unless it's too complicated. Seems we're still on track with that change aren't we ?

[carltongibson]

Yep. Let's have this as is for now. All green Travis 🎉 — that's worth the temporary compat check just for the aesthetic benefits over the autumn. 😃

Thanks @felixxm!

[xordoquy]

Unwanted side effect, it may trigger AppRegistryNotReady exceptions in some cases when DRF is imported in the models: it pulls the compat (more often than not) which pulls the authentication views which pull the user model which fails loading as models are not registered yet.

[edmorley]

Unwanted side effect, it may trigger AppRegistryNotReady exceptions

I've just opened #5564.

[rpkilby]

@edmorley - thanks, we'll continue the discussion over there.