fix(cache): redis backend uses async clients + real-redis CI

[wbarnha]

Description

Answers "can we test redis in CI?" — yes, and doing so surfaced that the redis cache backend was broken against a real server. This fixes it and adds the real-redis CI leg. Independent, off master. Supersedes #724 (its guard fix + test rewrite are folded in here; #724 is closed).

The bug (proven against a live redis)

The backend maps schemes to the synchronous redis.StrictRedis / redis.RedisCluster, but _get/_set/_delete/connect await the client:

>>> async with app.cache:
...     await app.cache.set("k", b"v", timeout=60)
TypeError: object bool can't be used in 'await' expression

It only ever looked fine because every unit test mocks the client with AsyncMock.

Fix — faust/web/cache/backends/redis.py

• Use the asyncio clients (redis.asyncio.StrictRedis / redis.asyncio.RedisCluster) so the awaited calls are real coroutines. Verified end-to-end against a live redis (set → get → overwrite → delete round-trip).
• Close the client on stop (on_stop → await client.aclose()) — the async client holds real connections.
• Bind redis = None (not just aredis) on ImportError, so the "not installed" guard raises ImproperlyConfigured instead of NameError.

Tests

• mocked_redis fixture now patches redis.asyncio.StrictRedis (the name the backend uses) and provides aclose.
• Test_RedisScheme + the not-installed test re-enabled, asserting the async client wiring.
• New real-redis integration tests (tests/integration/cache/), env-gated on FAUST_TEST_REDIS (skip when no server is reachable, like the broker suite), exercising set/get/overwrite/delete/missing against a live server. A conftest fixture reaps the loop's default-executor thread so the strict hygiene guards stay green.

CI

New test-redis-integration job with a redis:7 service container runs the integration tests against a real server. Advisory (not in the required check gate), matching the Kafka integration job — easy to promote to required later since, unlike the broker, redis is deterministic.

Verification

Unit test_cache.py (32) + integration tests/integration/cache (2) → 34 passed; the integration tests skip cleanly with no reachable redis; flake8/black/isort clean. redis is already in requirements/test.txt (via extras/redis.txt), so the CI job installs it.

🤖 Generated with Claude Code

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Generated by Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 80.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 94.84%. Comparing base (aa75db0) to head (7015cb1).

Files with missing lines	Patch %	Lines
faust/web/cache/backends/redis.py	80.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@                         Coverage Diff                         @@
##           claude/fix-715-cibuildwheel-314     #725      +/-   ##
===================================================================
+ Coverage                            94.81%   94.84%   +0.02%     
===================================================================
  Files                                  104      104              
  Lines                                11154    11158       +4     
  Branches                              1202     1203       +1     
===================================================================
+ Hits                                 10576    10583       +7     
+ Misses                                 482      479       -3     
  Partials                                96       96              

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