D2596: state: raise ProgrammingError if an invalid key is being accessed

[durin42 (Augie Fackler)]

durin42 added a comment.


  Hmm, really? Do any states have optional entries that would make this awkward?

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D2596

To: pulkit, #hg-reviewers
Cc: durin42, mercurial-devel