Don't know how many people are still tracking this, but this error is random and I haven't been able to figure out why. I have loaded my 2 test boxes over 25 times and on some installs I get this error and on others I don't. The posted fixes don't work as well.
Here is what I have found will fix it temporarily.
Do a /sbin/e-smith/config show horde DbPassword, then go into mysql and type grant all on horde.* to horde identified by '{password from above command}'; then reboot the server. You should see that 50turba_upgrade_1.1_to_1.2 will load ok this time. BUT, the next time you do a /sbin/e-smith/signal-event post-upgrade, this will return the error above and those steps need to be done again. The above has worked for me everytime I have had the failed error. Hopefully, this info can help someone else spot how to totally fix this. This problem was posted in the bugs section, but I think it has been closed with the resolution that was given. I still see this as a bug. If anyone else can confirm that the above works for them, the I can see about getting this bug re-opened to be looked at.