Redmine

The redmine:migrate_from_mantis and redmine:migrate_from_trac rake tasks are no longer maintained and are not usable in current Redmine versions.

Instead of keeping these tasks available as if they still work, they should fail immediately with a clear error message explaining that they are no longer maintained and cannot be used. The message should also state that these tasks will be removed in a future version of Redmine.

This would prevent confusion for users and make the current status of these tasks explicit.