[debian-mysql] Bug#864607: noisy mariadb-server-10.1 installation

[Juha Heinanen]

Package: mariadb-server-10.1
Version: 10.1.23-9+deb9u1

During 'apt-get dist-upgrade' from jessie to stretch, this got printed
to console:

Setting up mariadb-common (10.1.23-9+deb9u1) ...
Selecting previously unselected package mariadb-server-10.1.
(Reading database ... 72727 files and directories currently installed.)
Preparing to unpack .../mariadb-server-10.1_10.1.23-9+deb9u1_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.

Please fix so that the deprecated info does not get printed.  If every
package would be as noisy, user couldn't comprehend anything about what
is going on.

-- Juha