mozilla/zamboni — pull request #1630 by vinyll (2014-01-14 15:47:06+00:00)
Title: attempting to fix Http404 has_header calls (bug 951355)

As mentioned in [bug 951355](https://bugzilla.mozilla.org/show_bug.cgi?id=951355) Sentry reports lots of errors about Http404 having no `has_header`.
This could also fix https://bugzilla.mozilla.org/show_bug.cgi?id=873550.