old_people = set(a.user for a in m.acl)
for removed in old_people - people:
ma = [x for x in m.acl if x.user == removed][0]
ctx.current.delete(ma)
for p in people - old_people:
old_people = set(a.user for a in m.acl)
for removed in old_people - people:
ma = [x for x in m.acl if x.user == removed][0]
ctx.current.delete(ma)
for p in people - old_people: