'apt-get build-deb' fails when any "deb-src" repository is unreachable

Binary package hint: apt

This is highly related to bug #85590 and seems to have the same cause and/or relevant affected code.

To reproduce:
1. Add a non-existing repo in /etc/apt/sources.list
2. apt-get update. It will complain that the repo doesn't exist but it should be fine. apt-get install etc. can work
3. build-dep doesn't

$ sudo apt-get build-dep glipper
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Could not open file /var/lib/apt/lists/opensync.gforge.punktart.de_repo_opensync-0.21_dists_hardy_main_source_Sources - open (2 No such file or directory)