until today autopkgtests could only access *.ubuntu.com and
*.launchpad.net, attempts to access other internet sites hung. As we
need it for some tests (like the new ubuntu-developer-tools-center), I
now enabled proxy access. I. e. the test VMs have $http_proxy,
$https_proxy, and $no_proxy set correctly now, so that e. g. gem2deb 
It's possible though that some libraries/packages are buggy wrt.
handling proxies. So if you receive a "Jenkins Failed" mail for a
package of your's and there hasn't been an obvious change, this proxy
change might cause it.
As usual I'm reviewing all autopkgtest failures anyway and deal with
those which are due to the infrastructure, but I wanted to give an
advance warning to avoid wasting debugging time.
Martin Pitt | http://www.piware.de
Ubuntu Developer (www.ubuntu.com) | Debian Developer (www.debian.org)