Bug#1114899: debootstrap: output of --print-debs includes unexpected data

[cacin@allfreemail.net]

Package: debootstrap
Version: 1.0.141
Severity: normal

Dear Maintainer,

executing deboostrap and asking it to just print the list of packages that
would be downloaded and installed, and redirecting stdout to a log file:

```
# debootstrap --print-debs --arch=amd64 trixie /trixie-chroot https://deb.debian.org/debian >out.log
```

results in the following out.log:

```
04B54C3CDCA79751B16BC6B5225629DF75B188BD
41587F7DB8C774BCCF131416762F67A0B2C39DE4
B8B80B5B623EAB6AD8775C45B7C5D7D6350947F8

apt
base-files
base-passwd
bash
bsdutils
coreutils
dash
debconf
debian-archive-keyring
debianutils
diffutils
dpkg
findutils
gcc-14-base
grep
gzip
hostname
init-system-helpers
libacl1
libapt-pkg7.0
libattr1
libaudit-common
libaudit1
libblkid1
libbsd0
libbz2-1.0
libc-bin
libc6
libcap-ng0
libcap2
libcrypt1
libdb5.3t64
libdebconfclient0
libgcc-s1
libgmp10
libhogweed6t64
liblastlog2-2
liblz4-1
liblzma5
libmd0
libmount1
libnettle8t64
libpam-modules
libpam-modules-bin
libpam-runtime
libpam0g
libpcre2-8-0
libseccomp2
libselinux1
libsemanage-common
libsemanage2
libsepol2
libsmartcols1
libsqlite3-0
libssl3t64
libstdc++6
libsystemd0
libtinfo6
libudev1
libuuid1
libxxhash0
libzstd1
login
login.defs
mawk
mount
ncurses-base
ncurses-bin
openssl-provider-legacy
passwd
perl-base
sed
sqv
sysvinit-utils
tar
tzdata
util-linux
zlib1g adduser apt-utils ca-certificates cpio cron cron-daemon-common debconf-i18n dhcpcd-base dmidecode e2fsprogs fdisk ifupdown init iproute2 iputils-ping kmod less libapparmor1 libbpf1 libcap2-bin libcom-err2 libedit2 libelf1t64 libext2fs2t64 libfdisk1 libgssapi-krb5-2 libidn2-0 libjansson4 libk5crypto3 libkeyutils1 libkmod2 libkrb5-3 libkrb5support0 liblocale-gettext-perl libmnl0 libncursesw6 libnewt0.52 libnftables1 libnftnl11 libpopt0 libproc2-0 libreadline8t64 libslang2 libss2 libsystemd-shared libtext-charwidth-perl libtext-iconv-perl libtext-wrapi18n-perl libtirpc-common libtirpc3t64 libunistring5 libxtables12 linux-sysctl-defaults logrotate logsave nano netbase nftables openssl procps readline-common sensible-utils systemd systemd-sysv udev vim-common vim-tiny whiptail 
```

Notice that the first 3 lines of the log file are not names of packages, but
instead output of some signature verification. This should not be present in
the file, instead it should be part of stderr output like the other messages
from debootstrap.

Additionally, notice how the end of the log file has packages separated by
spaces instead of newlines, but this was already reported in
https://bugs.debian.org/1071651