6ff888bd2c
Fixes `Rack::Lint::LintError: a header value must be a String, but the value of 'Retry-After' is a Integer`. (see: https://github.com/rack/rack/blob/14a236b4f0899e46bc41c4f80dcff29159a59312/lib/rack/lint.rb#L676) I found it when I got flooded by those warning a while back in a test-related accident 😉 (ember CLI tests were hitting a local rails server at a fast rate)