run-tests: set attributes in sorted order
Python 3.8 preserves insertion order in serialized output
(https://bugs.python.org/issue34160). Older Pythons serialized
in sorted order.
Let's make insertion order sorted so behavior is consistent across
Python versions.
Differential Revision: https://phab.mercurial-scm.org/D5831
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}