Bug#638856: [pbuilder] fails to create with option --distribution experimental

[Ansgar Burchardt]

This might be caused by

  APT::Default-Release "experimental";

in apt.conf which pbuilder seems to add for a experimental chroot.
Doing this is wrong as it will cause all dependencies to be taken from
experimental, including those having a high enough version in unstable.

In particular I heard that pbuilder currently tries to install perl 5.16
from experimental (perl 5.16 is not really installable).

Ansgar