[issue18299] Change script_helper to use universal_newlines=True in _assert_python

[hai shi]

hai shi <shihai1991 at 126.com> added the comment:

spawn_python in script_helper is good enough, so this bug looks like cloud be closed.

----------

_______________________________________
Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue18299>
_______________________________________