fix: use REST API for team resolution (team_by_slug missing in github3.py v4.0.1)

[zkoppert]

Problem

get_team_members() in auth.py calls organization.team_by_slug(slug), but this method does not exist in github3.py v4.0.1. The call raises an AttributeError that gets caught by the broad except block, displaying just "team_by_slug" as the error - which is misleading since it suggests a permissions issue.

Root cause

github3.py v4.0.1 has these team methods on Organization:

• team(id) - lookup by numeric ID
• team_by_name(slug) - lookup by slug (misleading name, actually hits GET /orgs/{org}/teams/{slug})
• teams() - list all teams

There is no team_by_slug. It was requested in github3.py#948 but the maintainer shipped it as team_by_name instead. The method never existed in any released version.

How we found this

Debugged in github/new-user-experience where FILTER_TEAMS was configured:

1. Added a curl debug step before the Docker action to test the token against the Teams API
2. curl returned HTTP 200 - the token and endpoint work fine
3. Inside the container, github3.py raised AttributeError("team_by_slug")
4. Confirmed locally: "team_by_slug" in dir(github3.orgs.Organization) → False
5. Found the fix: "team_by_name" in dir(github3.orgs.Organization) → True, and inspecting the source shows it takes a slug and hits the same endpoint

Debug run: https://github.com/github/new-user-experience/actions/runs/23080465650/job/67048787353

Why tests did not catch this

The existing tests use MagicMock() which auto-creates any attribute accessed on it. So mock_org.team_by_slug.return_value = mock_team worked perfectly in tests - MagicMock happily faked a method that does not exist on the real class.

Added a guard test that checks the real github3.orgs.Organization class directly to prevent this class of bug in the future.

Fix

• auth.py: Replace organization.team_by_slug(team_slug) with organization.team_by_name(team_slug)
• test_auth.py: Update mocks to use team_by_name + add a guard test verifying the method exists on the real class

Local testing

Ran the action locally with DRY_RUN=true against github/new-user-experience:

Single team:

Resolving FILTER_TEAMS...
  Resolved team github/nux-reviewers: 6 member(s)
Combined 18 FILTER_AUTHORS + team members = 20 unique author(s)

Scanning github/new-user-experience...
  Found 3 open PRs, analyzing for conflicts...
  ✅ No conflicts detected

Multiple teams:

Resolving FILTER_TEAMS...
  Resolved team github/nux-reviewers: 6 member(s)
  Resolved team github/pull-requests-reviewers: 22 member(s)
Combined 18 FILTER_AUTHORS + team members = 35 unique author(s)

Scanning github/new-user-experience...
  Found 3 open PRs, analyzing for conflicts...
  ✅ No conflicts detected

Both teams that previously failed with team_by_slug now resolve correctly.

CI

• All 204 tests pass (99% coverage)
• make lint clean (pylint 10.00/10, mypy clean, black formatted)