# File lib/mechanize/http/auth_challenge.rb, line 35
    def realm uri
      case scheme
      when 'Basic' then
        raise ArgumentError, "provide uri for Basic authentication" unless uri
        Mechanize::HTTP::AuthRealm.new scheme, uri + '/', self['realm']
      when 'Digest' then
        Mechanize::HTTP::AuthRealm.new scheme, uri + '/', self['realm']
      else
        raise Mechanize::Error, "unknown HTTP authentication scheme #{scheme}"
      end
    end