Ubuntu 13.10 failed Redmine upgrade

When I upgraded Redmine from version 1.4.4 to 2.3.1-1 on Ubuntu 13.10 during a system upgrade (aptitude upgrade), I get the following error message:

Setting up redmine (2.3.1-1) ...
Inconsistent link in vendor/rails, please remove manually
rake aborted!
ERROR: 'rake/rdoctask' is obsolete and no longer supported. Use 'rdoc/task' (available in RDoc 2.4.2+) instead.

(See full trace by running task with --trace)
dpkg: error processing redmine (--configure):
 subprocess installed post-installation script returned error exit status 1
Errors were encountered while processing:
 redmine
E: Sub-process /usr/bin/dpkg returned an error code (1)
A package failed to install. Trying to recover:
Setting up redmine (2.3.1-1) ...
Inconsistent link in vendor/rails, please remove manually
rake aborted!
ERROR: 'rake/rdoctask' is obsolete and no longer supported. Use 'rdoc/task' (available in RDoc 2.4.2+) instead.

(See full trace by running task with --trace)
dpkg: error processing redmine (--configure):
 subprocess installed post-installation script returned error exit status 1
Errors were encountered while processing:
 redmine

Any ideas how to solve this?

Thanks in advance.