url(r'^staff/', include('staff.urls')),

urlpatterns = patterns('',
    # List View
    url(r'^$', StaffListView.as_view(), name="staffmember_list"),
    # Detail View
    url(r'^(?P<slug>[^/]+)/$', StaffDetailView.as_view(), name='staffmember_detail'),
)

Using the URLconf defined in my.urls, Django tried these URL patterns, in this order:
^media/(?P<path>.*)$
^static\/(?P<path>.*)$
^ru/ ^admin/
^ru/ ^sitemap\.xml$
^ru/ ^select2/
^ru/ ^ ^(?P<slug>[0-9A-Za-z-_.//]+)/$ [name='pages-details-by-slug']
^ru/ ^ ^$ [name='pages-root']
^ru/ ^staff/ ^$ [name='staffmember_list']
^ru/ ^staff/ ^(?P<slug>[^/]+)/$ [name='staffmember_detail']
The current URL, /ru/staff/, didn't match any of these.
You're seeing this error because you have DEBUG = True in your Django settings file. Change that to False, and Django will display a standard 404 page.