This has been fixed in debian package :
redmine (1.0.0-4) unstable; urgency=low
* If package redmine-<dbtype> is not installed, display a postinst debconf note and do not configure that db instance. (Closes: #590695)
and
redmine (1.0.1-1) unstable; urgency=low
* Postinst note should be an error. (Closes: #591220)
This has been fixed in debian package :
redmine (1.0.0-4) unstable; urgency=low
* If package redmine-<dbtype> is not installed, display a postinst
debconf note and do not configure that db instance. (Closes: #590695)
and
redmine (1.0.1-1) unstable; urgency=low
* Postinst note should be an error. (Closes: #591220)