I've pushed a change in autobuild that was dependent on a "recent
enough" version of dpkg-architecture. It breaks if the version is too
old. 1.5.48 and 1.5.49 are both broken. 1.5.50 is fixed.

As it *really* breaks autobuild/autoproj, you will need to upgrade
manually to 1.5.50. This is done simply with

gem install autobuild

In general, when this happens, to downgrade to an older version, you
would need to use the gem command as well:

gem install -v VERSION autobuild

The list of available versions is given by

gem search -a --remote autobuild

You would also need to reconfigure autoproj to not care about the ruby
osdeps until the fixed version is published (with autoproj reconfigure)