Updates a postgres role.

def _role_update(name,
                 user=None,
                 host=None,
                 port=None,
                 maintenance_db=None,
                 password=None,
                 createdb=None,
                 typ_='role',
                 createroles=None,
                 inherit=None,
                 login=None,
                 connlimit=None,
                 encrypted=None,
                 superuser=None,
                 replication=None,
                 rolepassword=None,
                 valid_until=None,
                 groups=None,
                 runas=None):
    '''
    Updates a postgres role.
    '''
    role = role_get(name,
                    user=user,
                    host=host,
                    port=port,
                    maintenance_db=maintenance_db,
                    password=password,
                    runas=runas,
                    return_password=False)

    # check if user exists
    if not bool(role):
        log.info(
            '%s \'%s\' could not be found', typ_.capitalize(), name
        )
        return False

    sub_cmd = 'ALTER ROLE "{0}" WITH'.format(name)
    sub_cmd = '{0} {1}'.format(sub_cmd, _role_cmd_args(
        name,
        encrypted=encrypted,
        login=login,
        connlimit=connlimit,
        inherit=inherit,
        createdb=createdb,
        createroles=createroles,
        superuser=superuser,
        groups=groups,
        replication=replication,
        rolepassword=rolepassword,
        valid_until=valid_until,
        db_role=role
    ))
    ret = _psql_prepare_and_run(['-c', sub_cmd],
                                runas=runas, host=host, user=user, port=port,
                                maintenance_db=maintenance_db,
                                password=password)

    return ret['retcode'] == 0