Backport of #50132 to lts/1.108.x. The line had no _prisma_error_code helper (main got it in #49190), so it is added here verbatim for db_write_never_sent.
Cherry-picked from b080c59e78 (main). Conflict in tests/unit/proxy/db/test_exception_handler.py resolved by keeping only the tests this PR adds, the two neighbouring tests from #49190 are not on this line.
Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>