Duplicate reviewer roles block assignments

Describe the issue

If a reviewer has more than one "reviewer" role for a review team tied to the same email address, attempting to assign a review to them results in a MultipleObjectsReturned exception.

If the same person has multiple roles with different email addresses for each, there is no problem.

The issue arises, I believe, due to the filtering done in AbstractReviewerQueuePolicy.setup_reviewer_fields() which, if multiple Role objects exist, can cause duplicate PKs in the reviewer field's queryset.

A quick fix by adding a distinct filter should fix this. We may want to add a uniqueness constraint for Role to prevent the initial situation from arising. It is not clear in this case exactly how the duplicate roles were created, but the Roles for the affected review team were recently adjusted by two chairs for a user who had multiple addresses. It seems likely that interleaved edits led to the inconsistent state.

Code of Conduct

• I agree to follow the IETF's Code of Conduct

Aggregated with agent assistance on 2026-08-18

Start at AbstractReviewerQueuePolicy.setup_reviewer_fields(), which the issue identifies as the source of duplicate primary keys in the reviewer queryset. Reproduce the case with multiple reviewer Role objects sharing an email address, then verify that assigning a review no longer raises MultipleObjectsReturned; the issue names no file or test to run.