How to setup http proxy with required authentication for sbaz?

How to setup a http proxy with required authentication for sbaz?

From http://www.scala-lang.org/node/6628
>>>
Firewalls and HTTP Proxies

Scala Bazaars uses HTTP to communicate with universe servers. If your
network blocks HTTP access, then, you need to configure sbaz to use an
HTTP proxy. To do this, create a file named config/sbaz.properties in
your managed directory and give it the appropriate proxy settings,
something like:

http.proxySet=true
http.proxyHost=localhost
http.proxyPort=3128
<<<
but there is no words how to pass authentication credentials
(username, password) to this proxy.

I looked at sbaz sources. It seems like sbaz.properties is simply
loaded to JVM system properties map and there is not any
java.net.Authenticator for proxy host. May be I missed something.