Bug#888709: debootstrap: Silently fails if the target directory exists and is not empty.

[Mike Hommey <mh+reportbug@glandium.org>]

Package: debootstrap
Version: 1.0.89
Severity: normal

Dear Maintainer,

I was running sbuild-createchroot, and it failed with:
I: Chosen extractor for .deb packages: dpkg-deb
I: Extracting libacl1...
E: Error running debootstrap at /usr/sbin/sbuild-createchroot line 268.

Turns out that was happening because the target directory existed and
was not empty.

But neither debootstrap nor sbuild-createchroot printed out something
useful. Debootstrap surely shouldn't fail without saying what went
wrong.

Mike