[issue22173] Update lib2to3.tests and test_lib2to3 to use test discovery

[Ezio Melotti]

Ezio Melotti added the comment:

LGTM

----------
nosy: +ezio.melotti
stage: patch review -> commit review

_______________________________________
Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue22173>
_______________________________________