From what I've seen online, definitely looks like scale rot. Main causes of it tend to be wet or dirty bedding. If they spend too much time crawling over uncleaned excrement, it can get inbetween their scales and cause rot. Also, I've read of cases that highly scented or improper substrate may act as an irritant for the snake. No cedar or pine bark are the only ones I remember off hand. What Zeion said may also be true: improper temps and the snake's inability to regulate its body temperature often cause death. When I bought my python, the lady that sold her to me told me to use bulbs instead of UTH because she's lost one of her own due to belly burn

I am sorry for your loss, the only advice I can give you is to double and triple check your husbandry and take your python to the vet immediately. Don't risk another death.