apt-get fails with "system" message bus problem

[Malte Forkel <malte.forkel@berlin.de>]

Hello!

Two weeks ago I posted the following question on Debian User. Since
nobody on that list could help, I'm now trying my luck here. I'm sorry
should you have already seen this before...

I have written a little script to download a package from a repository
specified on the command line. E.g. the following will download the
package debian-archive-keyring_2010.08.28_all.deb on an Ubuntu system:

$ apt-getfrom -s "deb http://ftp.debian.org/debian stable main" \
download debian-archive-keyring

apt-getfrom works by setting up a "sandbox" environment in a temporary
configuration file, based on a suggestion by Bob Proulx (see
http://lists.debian.org/debian-user/2012/04/msg00953.html)

When I use apt-getfrom while building a package (i.e. from within
debian/rules), I run into an error. I guess it has to do with fakeroot,
because I can reproduce the problem like this:

$ fakeroot apt-getfrom -s "deb http://ftp.debian.org/debian stable \
main" download debian-archive-keyring
Failed to open connection to "system" message bus: Did not receive a
reply. Possible causes include: the remote application did not send a
reply, the message bus security policy blocked the reply, the reply
timeout expired, or the network connection was broken.

Could someone please explain what causes this error and/or how to avoid it?

Thanks,
Malte