fix(urls): update 4xx error pages preview, to accept exceptions

closes #444

CHANGELOG.md

@@ -2,6 +2,9 @@
 All enhancements and patches to cookiecutter-django will be documented in this file.
 This project adheres to [Semantic Versioning](http://semver.org/).
 
+## [2015-12-16]
+- Update preview 4xx error pages to accept `exception` argument (@theskumar)
+
 ## [2015-12-15]
 ### Changed
 - Fix celery worker app name in Procfile (@stepmr)

{{cookiecutter.repo_name}}/config/urls.py

@@ -28,8 +28,8 @@ if settings.DEBUG:
     # This allows the error pages to be debugged during development, just visit
     # these url in browser to see how these error pages look like.
     urlpatterns += [
-        url(r'^400/$', default_views.bad_request),
-        url(r'^403/$', default_views.permission_denied),
-        url(r'^404/$', default_views.page_not_found),
+        url(r'^400/$', default_views.bad_request, kwargs={'exception': Exception("Bad Request!")}),
+        url(r'^403/$', default_views.permission_denied, kwargs={'exception': Exception("Permissin Denied")}),
+        url(r'^404/$', default_views.page_not_found, kwargs={'exception': Exception("Page not Found")}),
         url(r'^500/$', default_views.server_error),
     ]