class method self.const_missing

# File actionpack/lib/action_dispatch/http/mime_type.rb, line 48
    def const_missing(sym)
      ext = sym.downcase
      if Mime[ext]
        ActiveSupport::Deprecation.warn(<<-MSG.squish)
          Accessing mime types via constants is deprecated.
          Please change `Mime::#{sym}` to `Mime[:#{ext}]`.
        MSG
        Mime[ext]
      else
        super
      end
    end