token_metadata_enabled=False now requires broadcast_address and listen_address in system.local

[dkropachev]

Problem

695a68932f9dfc14293e4b4c868e367740d93244 (issue #1008) factored the local-metadata column
list into _SELECT_LOCAL_COLUMNS and reused it for both local queries:

python-driver/cassandra/cluster.py

Lines 3808 to 3812 in d0d5378

	_time = time
	def __init__(self, cluster, timeout,
	schema_event_refresh_window,
	topology_event_refresh_window,

Before that commit the two queries had deliberately different column sets:

_SELECT_LOCAL = "SELECT broadcast_address, cluster_name, data_center, host_id, listen_address, partitioner, release_version, rpc_address, schema_version, tokens FROM system.local WHERE key='local'"
_SELECT_LOCAL_NO_TOKENS = "SELECT host_id, cluster_name, data_center, rack, partitioner, release_version, schema_version, rpc_address FROM system.local WHERE key='local'"

_SELECT_LOCAL_NO_TOKENS omitted broadcast_address and listen_address; it now requests
both. It is used whenever token_metadata_enabled=False (cassandra/cluster.py:4133 and
cassandra/cluster.py:4293).

Impact

Against a server whose system.local does not expose those two columns — a proxy, emulator,
or managed service with a reduced system.local — metadata refresh now fails with a
server-side InvalidRequest instead of succeeding. token_metadata_enabled=False was the
only configuration that avoided asking for them.

Confidence

Low, and this should be triaged before any work happens. Arguments against it mattering:

• _SELECT_LOCAL already requested both columns, so only a deployment that needs
  token_metadata_enabled=False to connect at all is affected.
• The reduced list came in with d4bf4026 (PYTHON-327, "Cluster config to disable schema and
  token processing"), whose stated goal was skipping token processing on large clusters — not
  compatibility with a limited system.local. The narrow column set may have been incidental
  rather than deliberate.

So this may be purely theoretical. Worth a decision either way, since the previous asymmetry
is the kind of thing that is easy to reintroduce by accident.

Note that #1008's fix assigns host.listen_address from the local row
(cassandra/cluster.py:4398), so a no-tokens path that stopped selecting the column would
leave it None — which is what it did before 695a6893, but the interaction should be
confirmed rather than assumed.

Notes

Found during review of PR #1025; out of that PR's scope (695a6893 is already on master,
and #1008 is closed).