ci: use psycopg 3 for the PostgreSQL database tests

[WilliamBergamin]

Summary

Fixes the nightly Database Unit Tests regression on main (https://github.com/slackapi/python-slack-sdk/actions/runs/36079341012/job/107897544636).

SQLAlchemy 2.1.0 (released 2026-09-24) changed the default PostgreSQL driver for bare postgresql:// URLs from psycopg2 to psycopg (v3). Our requirements/optional.txt range (SQLAlchemy>=2.0.52,<3) picked it up. The sync PostgreSQL step used a bare URL but requirements/databases.txt only installed psycopg2-binary, so every test errored in setUp with ModuleNotFoundError: No module named 'psycopg'.

This is not a code regression. The failing run is on the same commit as the last green main build, and the SQLite store tests already pass on SQLAlchemy 2.1.0 in the unit test matrix.

Changes:

• requirements/databases.txt: psycopg2-binary -> psycopg[binary]>=3.3.6,<4.
• ci-build.yml: TEST_DATABASE_URL now names the driver explicitly (postgresql+psycopg://), the form SQLAlchemy's migration guide recommends. The job no longer depends on SQLAlchemy's default, and the explicit URL works on 2.0 and 2.1. The async URL already said postgresql+asyncpg:// and is unchanged.

Possible follow-ups, not in this PR:

• integration_tests/samples/token_rotation/oauth_sqlalchemy.py and oauth_sqlite3.py suggest postgresql:// with pip install psycopg2 in a comment. On SQLAlchemy 2.1 that combination hits this same error.
• The dependencies list in AGENTS.md doesn't mention requirements/databases.txt.

Testing

Locally, on Python 3.14.7 with SQLAlchemy 2.1.0 against a local PostgreSQL 16:

• Before (main's requirements and URL): tests/slack_sdk/oauth/installation_store/test_sqlalchemy.py fails 5/5 with the same No module named 'psycopg' as CI.
• After (psycopg2-binary uninstalled, this branch's databases.txt, CI's env vars): all four PostgreSQL suites pass.
  • Sync, psycopg 3: installation_store 5/5, state_store 3/3.
  • Async, asyncpg: installation_store 5/5, state_store 3/3.

The state_store sync tests and both async suites never ran in the failing job (the step stopped at the first failure). The Database Unit Tests job on this PR is the check that the whole job is green again.

No Python code changed, so I didn't run ./scripts/run_validation.sh locally. The rest of the CI matrix covers it.

Category

• slack_sdk.web.WebClient (sync/async) (Web API client)
• slack_sdk.webhook.WebhookClient (sync/async) (Incoming Webhook, response_url sender)
• slack_sdk.socket_mode (Socket Mode client)
• slack_sdk.signature (Request Signature Verifier)
• slack_sdk.oauth (OAuth Flow Utilities)
• slack_sdk.models (UI component builders)
• slack_sdk.scim (SCIM API client)
• slack_sdk.audit_logs (Audit Logs API client)
• slack_sdk.rtm_v2 (RTM client)
• /docs (Documents)
• /tutorial (PythOnBoardingBot tutorial)
• tests/integration_tests (Automated tests for this library)

Requirements

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.
• I've run python3 -m venv .venv && source .venv/bin/activate && ./scripts/run_validation.sh after making the changes.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.15%. Comparing base (77d0a1a) to head (9ab7f2f).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1971   +/-   ##
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  Coverage   84.15%   84.15%           
=======================================
  Files         118      118           
  Lines       13566    13566           
=======================================
  Hits        11416    11416           
  Misses       2150     2150           

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[AmyScript]

LGTM! Thanks for the fix!