return nil, err
			}
			nonExistentUsers = append(nonExistentUsers, ndn.String())
		}
	}
	return nonExistentUsers, nil
}

// LookupGroupMemberships - for each DN finds the set of LDAP groups they are a
// member of.
func (l *Config) LookupGroupMemberships(userDistNames []string, userDNToUsernameMap map[string]string) (map[string]set.StringSet, error) {
	conn, err := l.LDAP.Connect()
	if err != nil {