From a fresh Python3.2.1 tarball:

nneonneo@nneonneo-mbp:~/devel/Python-3.Lib/test$ for i in tokenize_tests-*; do echo $i; xxd $i | head -n 1; done
tokenize_tests-latin1-coding-cookie-and-utf8-bom-sig.txt
0000000: efbb bf23 202d 2a2d 2063 6f64 696e 673a  ...# -*- coding:
tokenize_tests-no-coding-cookie-and-utf8-bom-sig-only.txt
0000000: efbb bf23 2049 4d50 4f52 5441 4e54 3a20  ...# IMPORTANT: 
tokenize_tests-utf8-coding-cookie-and-no-utf8-bom-sig.txt
0000000: efbb bf23 202d 2a2d 2063 6f64 696e 673a  ...# -*- coding:
tokenize_tests-utf8-coding-cookie-and-utf8-bom-sig.txt
0000000: efbb bf23 202d 2a2d 2063 6f64 696e 673a  ...# -*- coding:

From this, it appears that the file called "tokenize_tests-utf8-coding-cookie-and-no-utf8-bom-sig.txt" actually has a UTF-8 BOM signature, which means either the comment is lying or the BOM was accidentally added to the test file at some point.

It looks like a BOM has been present in that file for a *long* time: it is there in the Python 3.0 source tarball, and, according to the converted svn-to-hg history, it was there in its original check-in and is still there in the current development tip.

Yes, it seems that way. Then the question is: why does the comment claim that it doesn't have a BOM?

Also, test_tokenize.py is wrong around line 651:

    def test_utf8_coding_cookie_and_no_utf8_bom(self):
        f = 'tokenize_tests-utf8-coding-cookie-and-utf8-bom-sig.txt'
        self.assertTrue(self._testFile(f))

It reads the wrong file in this case, judging by the testcase name. (This makes it a duplicate of the test_utf8_coding_cookie_and_utf8_bom case)

Attached is a patch which fixes this. Python 3.2.1 still passes the test after applying the patch, as expected.

New changeset 0c254698e0ed by Ned Deily in branch '3.2':
Issue #12587: Correct faulty test file and reference in test_tokenize.
http://hg.python.org/cpython/rev/0c254698e0ed

New changeset c1d2b6b337c5 by Ned Deily in branch 'default':
Issue #12587: Correct faulty test file and reference in test_tokenize.
http://hg.python.org/cpython/rev/c1d2b6b337c5

Thanks for the report and the patch!  Applied to 3.2 (for 3.2.2) and default (for 3.3).