[dtest] flakey test: test_decommissioned_node_cant_rejoin - topology_test.TestTopology

> assert re.search(rejoin_err,
 '\n'.join(['\n'.join(err_list) for err_list in node3.grep_log_for_errors()]), re.MULTILINE)
E AssertionError: assert None
E + where None = <function search at 0x7fa9540c4ea0>('This node was decommissioned and will not rejoin the ring', '', <RegexFlag.MULTILINE: 8>)
E + where <function search at 0x7fa9540c4ea0> = re.search
E + and '' = <built-in method join of str object at 0x7fa9553f1ea0>([])
E + where <built-in method join of str object at 0x7fa9553f1ea0> = '\n'.join
E + and <RegexFlag.MULTILINE: 8> = re.MULTILINE