Update how psycopg2 errors are referenced

[dhruvkb]

Description

This PR fixes the error raised in #1221, changing how a psycopg2 error is referenced, thus unblocking our upgrade to Django v4.2.

Testing Instructions

CI should pass.

Checklist

• My pull request has a descriptive title (not a vague title like
  Update index.md).
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• I added or updated tests for the changes I made (if applicable).
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[obulat]

Thank you for finding and fixing this

[AetherUnbound]

Good find!