[1.5.x] Fixed #20237 -- Reenabled assertContains with binary parameter

Thanks Baptiste Mispelon for the review.
Backport of fe01404bb9 from master.

tests/regressiontests/test_client_regress/urls.py

@@ -28,6 +28,7 @@ urlpatterns = patterns('',
     (r'^check_session/$', views.check_session_view),
     (r'^request_methods/$', views.request_methods_view),
     (r'^check_unicode/$', views.return_unicode),
+    (r'^check_binary/$', views.return_undecodable_binary),
     (r'^parse_unicode_json/$', views.return_json_file),
     (r'^check_headers/$', views.check_headers),
     (r'^check_headers_redirect/$', RedirectView.as_view(url='/test_client_regress/check_headers/')),