Be more verbose about superusers

ssoauth/auth_utils.py

@@ -157,6 +157,7 @@ def update_user_compat_flags(user, check_login_perm=True):
     user_groups = user.groups.all()
     su_groups = get_superuser_groups()
     if bool(set(user_groups) & set(su_groups)):
+        logger.info("User {0} is superuser (has all permissions).".format(user))
         user.is_superuser = True
     # is_staff
     if user.has_perm(get_full_perm_name(STAFF_PERM_CODENAME)):