setup_upstream_proxy_authentication

# File lib/webrick/httpproxy.rb, line 262
    def setup_upstream_proxy_authentication(req, res, header)
      if upstream = proxy_uri(req, res)
        if upstream.userinfo
          header['proxy-authorization'] =
            "Basic " + [upstream.userinfo].pack("m").delete("\n")
        end
        return upstream
      end
      return FakeProxyURI
    end