Using the official MariaDB packages.
Upgraded from 10.1.23-MariaDB-1~jessie.
After the upgrade to 10.2.6+maria~jessie the following shows up when trying to start pureftpd:
libmysqlclient is a symlink to libmariadb.so.3 (as installed by the package). libmariadb is 10.2.6+maria~jessie.
As a result pureftpd (and I suspect others depending on that file) fail to start.