#25102 was merged recently and it contains a number of migrations with the exact same timestamp as some previously existing migrations in REX.

This causes an error when you upgrade a system where REX was installed before (db:migrate):

ActiveRecord::DuplicateMigrationVersionError:

Multiple migrations have the version number 20150616080015.

I can't see a reason why this wouldn't happen on production too during an upgrade, even if we remove the migrations from REX, the timestamps are still saved in memory.