trace.py in Python 3.3 standard library uses the _warn function without importing it. As a result, an attempt to use a now-deprecated function fails with a NameError:

> python3
Python 3.3.0 (v3.3.0:bd8afb90ebf2, Sep 29 2012, 01:25:11) 
[GCC 4.2.1 (Apple Inc. build 5666) (dot 3)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import trace
>>> trace.modname('')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/trace.py", line 827, in modname
    _warn("The trace.modname() function is deprecated",
NameError: global name '_warn' is not defined

Workaround: "import warnings; trace._warn = warnings.warn" after importing trace

Patch attached with tests.

Great patch with tests.

Eric, do you want to commit?

New changeset 3f8b5fcbf07e by Ezio Melotti in branch '3.3':
#17143: fix a missing import in the trace module.  Initial patch by Berker Peksag.
http://hg.python.org/cpython/rev/3f8b5fcbf07e

New changeset 46e9f668aea9 by Ezio Melotti in branch 'default':
#17143: merge with 3.3.
http://hg.python.org/cpython/rev/46e9f668aea9

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.

The windows buildbots are failing with the following error:
ERROR: test_deprecated_find_strings (test.test_trace.TestDeprecatedMethods)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:\buildbot.python.org\3.x.kloth-win64\build\lib\test\test_trace.py", line 401, in test_deprecated_find_strings
    trace.find_strings(fd.name)
  File "C:\buildbot.python.org\3.x.kloth-win64\build\lib\trace.py", line 850, in find_strings
    return _find_strings(filename, encoding=None)
  File "C:\buildbot.python.org\3.x.kloth-win64\build\lib\trace.py", line 422, in _find_strings
    with open(filename, encoding=encoding) as f:
PermissionError: [Errno 13] Permission denied: 'c:\\users\\buildbot\\appdata\\local\\temp\\tmp_08yph'

See:
http://buildbot.python.org/all/builders/AMD64%20Windows7%20SP1%203.3/builds/491/steps/test/logs/stdio
http://buildbot.python.org/all/builders/AMD64%20Windows7%20SP1%203.x/builds/1473/steps/test/logs/stdio

The problem seems to be related to the use of NamedTemporaryFile in test_deprecated_find_strings, but doesn't seem to affect test_deprecated_find_executable_linenos.

There's also a warning for test_ignored:
test_ignored (test.test_trace.Test_Ignore) ... Not printing coverage data for 'c:\\users\\buildbot\\appdata\\local\\temp\\tmpwrqs7_': [Errno 13] Permission denied: 'c:\\users\\buildbot\\appdata\\local\\temp\\tmpwrqs7_'

This was probably here already, but went unnoticed because it doesn't cause failures and it's probably printed in verbose mode only.

New changeset 662f97427acf by Ezio Melotti in branch '3.3':
#17143: fix buildbot failures on Windows.
http://hg.python.org/cpython/rev/662f97427acf

New changeset 1bf0ff7db856 by Ezio Melotti in branch 'default':
#17143: merge with 3.3.
http://hg.python.org/cpython/rev/1bf0ff7db856

This should be fixed now.