Running the linked sql script by hand fixed the problem. There is nothing in the logs to indicate why this change didn't take during the upgrade.
Jul 11 2019
Jul 5 2019
I am up to date with the Ubuntu 18.04 repo. For what its worth it looks like this has actually been fixed. I no longer have trouble with calendar invites.
May 19 2019
Mar 25 2019
Yes, I did import a calendar more than a year ago but have since deleted it.
Feb 15 2019
Duplicate of https://git.kolab.org/T5172
Nov 2 2017
For others who might run into the same issue, the above sql does not work. after fixing the syntax because md had interpreted the backticks, it left me unable to send or receive mail. I had to delete the table and let pykolab recreate it.
My kolab install is rejecting emails from Amazon because of this bug. The logs when such an email arrive show: