Fix "Pending migrations" log message
The listed migrations are now separated for readability.
Before: Pending migrations: 202012081724002021021610250020210223155000202103191604002021032516170020210511192000
After: Pending migrations: 20201208172400, 20210216102500, 20210223155000, 20210319160400, 20210325161700, 20210511192000