tests/test-dirstate-backup.t

context: stop catching TypeError when converting hex nodeid to binary

It has been a programming error to pass a 40-character string that is
not a hex nodeid since 8b86acc7aa64 (context: drop support for looking
up context by ambiguous changeid (API), 2018-04-28), so we can just
let it raise a TypeError.

Differential Revision: https://phab.mercurial-scm.org/D4807

Set up

  $ hg init repo
  $ cd repo

Try to import an empty patch

  $ hg import --no-commit - <<EOF
  > EOF
  applying patch from stdin
  abort: stdin: no diffs found
  [255]

No dirstate backups are left behind

  $ ls .hg/dirstate* | sort
  .hg/dirstate