The chord progression is i^o II iii iv V VI vii, which are the successive triads of a locrian scale, which is like a major scale but you start from the 7th note

The chord progression is i^o II iii iv V VI vii, which are the successive triads of a locrian scale, which is like a major scale but you start from the 7th note of the scale (ti). In this case, use A flat major, but start on G.