Comment 5 for bug 599695

So if you want to get the old behavior back of "not checking anything" security-wise, there is a new flag now and unsetting DEBOOTSTRAPOPTS in /etc/pbuilderrc will remove the new keyring bits.

Alternatively, to still get security, you can switch manually in /etc/pbuilderrc, or point pbuilder as alternate pbuilderrcs e.g. /etc/pbuilderrc-debian including the usual one but setting different DEBOOTSTRAPOPTS. Finally, you can pass --debootstrapopts directly too.

The proper solution is much longer to implement correctly.