tests/test-gendoc-zh_CN.t

debugbuilddag: use context manager for progress, locks, transaction

I minor side-effect is that .hg/localtags is now written before the
transaction commits.

Differential Revision: https://phab.mercurial-scm.org/D3777

#require docutils gettext

  $ $TESTDIR/check-gendoc zh_CN
  checking for parse errors