Bug#863479: perl-base should add Breaks: debconf (<< 1.5.57~)

[Adrian Bunk]

Package: perl-base
Version: 5.24.1-2
Severity: serious

Technically #786705 is just a harmless warning, but when
during a jessie -> stretch upgrade perl-base is upgraded
before debconf is upgraded the user might see a lot scary
warnings as if something was seriously broken.

Example with debconf 1.5.56 and perl-base 5.24.1-2 installed:

# apt-get install libpam-modules
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following additional packages will be installed:
  libpam-modules-bin
The following packages will be upgraded:
  libpam-modules libpam-modules-bin
2 upgraded, 0 newly installed, 0 to remove and 3 not upgraded.
Need to get 0 B/412 kB of archives.
After this operation, 18.4 kB disk space will be freed.
Do you want to continue? [Y/n] 
Unescaped left brace in regex is deprecated, passed through in regex; marked by <-- HERE in m/^(.*?)(\\)?\${ <-- HERE ([^{}]+)}(.*)$/ at /usr/share/perl5/Debconf/Question.pm line 72.
Unescaped left brace in regex is deprecated, passed through in regex; marked by <-- HERE in m/\${ <-- HERE ([^}]+)}/ at /usr/share/perl5/Debconf/Config.pm line 30.
Preconfiguring packages ...
(Reading database ... 10801 files and directories currently installed.)
Preparing to unpack .../libpam-modules-bin_1.1.8-3.5_amd64.deb ...
Unpacking libpam-modules-bin (1.1.8-3.5) over (1.1.8-3.1+deb8u2) ...
Setting up libpam-modules-bin (1.1.8-3.5) ...
(Reading database ... 10801 files and directories currently installed.)
Preparing to unpack .../libpam-modules_1.1.8-3.5_amd64.deb ...
Unescaped left brace in regex is deprecated, passed through in regex; marked by <-- HERE in m/^(.*?)(\\)?\${ <-- HERE ([^{}]+)}(.*)$/ at /usr/share/perl5/Debconf/Question.pm line 72.
Unescaped left brace in regex is deprecated, passed through in regex; marked by <-- HERE in m/\${ <-- HERE ([^}]+)}/ at /usr/share/perl5/Debconf/Config.pm line 30.
Unpacking libpam-modules:amd64 (1.1.8-3.5) over (1.1.8-3.1+deb8u2) ...
Setting up libpam-modules:amd64 (1.1.8-3.5) ...
Installing new version of config file /etc/security/namespace.init ...
Processing triggers for man-db (2.7.6.1-2) ...
#


perl-base should add a Breaks: debconf (<< 1.5.57~).