[issue21337] Add tests for Tix

[Zachary Ware]

New submission from Zachary Ware:

We should have some tests for Tix, which currently has none.  The Windows buildbots will be able to run the tests, but Tix is not guaranteed to be available elsewhere.

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components: Tests, Tkinter
keywords: easy
messages: 217089
nosy: zach.ware
priority: low
severity: normal
stage: needs patch
status: open
title: Add tests for Tix
type: enhancement
versions: Python 3.5

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue21337>
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