phabricator: use templatefilters.json in writediffproperties
Instead of json.dumps, since it makes the code simpler and more readable.
This would have been the better option for 8fd19a7b4ed6 but I wasn't aware of
it at the time.
Differential Revision: https://phab.mercurial-scm.org/D6295
commands: use byteskwargs() in verify()
Otherwise Python 3 complains about the missing key.
Differential Revision: https://phab.mercurial-scm.org/D6294