Comment 3 for bug 816155

This appears to be an issue with apt (or something even lower level), not sbuild. One can witness with a simple "apt-get install mail-transport-agent" followed by "apt-get install mail-transport-agent > foo" that the package list, while happily displayed on your console, isn't making it to STDOUT pipes, which sbuild needs to read them.

What's much more distressing is that strace shows the list being written to FD 1 (which vaguely matches with "hey, we can see it on the console"), so I have no idea why neither Perl nor the shell redirect get around to seeing it.