[SOLVED] Upgrade from 2.1.0 to 3.0.3 failed

I did two things:

• I filled the TeamMembers table with the contents from:
  SELECT Users.TeamId, Users.Id, Users.Roles WHERE Users.TeamId = $HERE_COMES_THE_TEAM_ID_THAT_THE_UPGRADE_PROCESS_COMPLAINS_ABOUT
• I set DeleteAT for every entry in the TeamMembers table to 0 (zero)
• ALTER TABLE TeamMembers DROP COLUMN DeleteAt

I'm not sure the first step was necessary, however, after that the upgrade command worked.