That looks like standard HTTP authentication (Basic/Digest).
You will need a regular HTTP client library in order to supply
like Httparty, HttpClient, Mechanize etc.
You might have better luck with Celerity ( a JRuby implementation of
that uses a pure java Http Client, instead of automating a browser) -
might expose methods for dealing with HTTP auth instead of form
There are a LOT of Ruby HTTP libraries out there - you might have to do
bit of homework
on them and their feature sets.
Also double check the Watir site. Popups of all kinds are a real
there, and they
have developed a couple of interesting workarounds. They might also
that I haven’t mentioned here.