[issue17143] trace.py uses _warn without importing it

[Ezio Melotti]

Ezio Melotti added the comment:

Fixed, thanks for the report and the patch!

I changed a couple of things:
1) test_deprecated_usage was printing the usage on stderr while running the tests -- I changed it to use a StringIO and added a minimal test to check that the usage is actually written;
2) there was an unnecessary "import warnings" that I removed;

FTR this bug was introduced in f1604371240a.

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assignee:  -> ezio.melotti
nosy: +flox
resolution:  -> fixed
stage: patch review -> committed/rejected
status: open -> closed

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue17143>
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