Use of uninitialized value in concatenation (.) or string at /usr/share/perl5/Debconf/DbDriver/File.pm line 44, <DEBCONF_CONFIG> chunk 3.
Use of uninitialized value in -e at /usr/share/perl5/Debconf/DbDriver/File.pm line 46, <DEBCONF_CONFIG> chunk 3.
Use of uninitialized value in pattern match (m//) at /usr/share/perl5/Debconf/DbDriver/File.pm line 47, <DEBCONF_CONFIG> chunk 3.
Use of uninitialized value $directory in -d at /usr/share/perl5/Debconf/DbDriver/File.pm line 48, <DEBCONF_CONFIG> chunk 3.
Use of uninitialized value $directory in concatenation (.) or string at /usr/share/perl5/Debconf/DbDriver/File.pm line 49, <DEBCONF_CONFIG> chunk 3.
debconf: DbDriver "config": mkdir :No such file or directory


caused by /var/cache/debconf directory not existing. solutions:

mkdir /var/cache/debconf
chmod 755 /var/cache/debconf

apt-get install debconf --reinstall