utils: Provide CallStack to expectJust
utils: Provide CallStack to expectJust

Test Plan: Validate

Reviewers: gridaphobe, austin

Reviewed By: austin

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2106

tjakway/ghcjvm,sgillespie/ghc,ezyang/ghc,shlevy/ghc,tjakway/ghcjvm,mettekou/ghc,sdiehl/ghc,vikraman/ghc,mettekou/ghc,snoyberg/ghc,sdiehl/ghc,sdiehl/ghc,vikraman/ghc,sdiehl/ghc,vTurbine/ghc,shlevy/ghc,ezyang/ghc,snoyberg/ghc,tjakway/ghcjvm,olsner/ghc,sdiehl/ghc,vikraman/ghc,snoyberg/ghc,snoyberg/ghc,olsner/ghc,ezyang/ghc,shlevy/ghc,sdiehl/ghc,tjakway/ghcjvm,mettekou/ghc,sgillespie/ghc,vTurbine/ghc,ezyang/ghc,sgillespie/ghc,snoyberg/ghc,tjakway/ghcjvm,mettekou/ghc,ezyang/ghc,vTurbine/ghc,shlevy/ghc,sgillespie/ghc,tjakway/ghcjvm,vTurbine/ghc,shlevy/ghc,snoyberg/ghc,vTurbine/ghc,olsner/ghc,tjakway/ghcjvm,sgillespie/ghc,sgillespie/ghc,vTurbine/ghc,olsner/ghc,ezyang/ghc,vikraman/ghc,sdiehl/ghc,shlevy/ghc,mettekou/ghc,mettekou/ghc,vikraman/ghc,sgillespie/ghc,vikraman/ghc,vikraman/ghc,vTurbine/ghc,olsner/ghc,mettekou/ghc,snoyberg/ghc,shlevy/ghc,ezyang/ghc,olsner/ghc,olsner/ghc