[nandanadileep]

Fixes #773.

Focused Python fix for: exists() depends on exact FT.INFO error wording; an unrecognised "missing index" message makes create() never create the index (regression from #672)

Changed implementation: redisvl/exceptions.py.
Regression tests: tests/unit/test_index_exists.py.

Verification (working directory .): .venv/bin/python -m pytest -q -x -p no:cacheprovider -- /workspace/tests/unit/test_index_exists.py

• Patched code: 14 tests, zero failures/errors.
• Original code with the same regression tests: 1 failures, zero collection/setup errors.
• Base commit: 1188d0a987aa2dfb415707522fa7fe95d2143255.

AI-assisted contribution: OpenCode using Autoloops wrote this patch. The automated harness independently ran the tests listed above. No human review is claimed.

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Note

Low Risk
Narrow change to error-string matching for absent indexes; slightly broader substring match but covered by existing non-missing-index regression tests.

Overview
Extends missing-index detection for FT.INFO failures so Valkey Search (e.g. ElastiCache) is treated like Redis Search when an index does not exist.

Adds the fragment "not found in database" to _MISSING_INDEX_ERROR_FRAGMENTS, covering messages such as Index with name '…' not found in database 0 where the index name sits between “index” and “not found” and the old "index not found" substring did not match. A parametrized unit test documents that wording so exists() returns False instead of surfacing an unclassified error—which after #672 could block create() from ever creating the index.

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