You can try this:
from django.contrib.sessions.models import Session
Session.Meta.db_table = 'my_session'
EDITED
The above solution throws an error but the following works:
from django.contrib.sessions.models import Session
Session._meta.db_table = "my_session"
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…