[3.10] bpo-44589: raise a SyntaxError when mapping patterns have duplicate literal keys (GH-27131) (GH-27157)



(cherry picked from commit 2693132292b2acf381ac6fa729bf3acf41d9d72b)


Co-authored-by: Jack DeVries <58614260+jdevries3133@users.noreply.github.com>

Automerge-Triggered-By: GH:brandtbucher
4 files changed