test_shutil.TestWhich.test_non_matching_mode fails when run as root

python3.3 is run under autopkgtest as root which makes the testcase test_shutil.TestWhich.test_non_matching_mode fails because the temporary file is always writeable:

To reproduce the failure run the command:

$ sudo python3.3 -E -Wd -tt /usr/lib/python3.3/test/regrtest.py -v -w test_shutil
[...]
======================================================================
FAIL: test_non_matching_mode (test.test_shutil.TestWhich)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/lib/python3.3/test/test_shutil.py", line 1334, in test_non_matching_mode
    self.assertIsNone(rv)
AssertionError: '/tmp/Tmpn3pl68/Tmp3w_zif.Exe' is not None

----------------------------------------------------------------------

Possible solutions:
  - Change which invocation to search for a file with 'execute' bit set
  - Set immutable attribute on the temporary file
  - Skip the test when executed as root

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: python3.3 3.3.1-1ubuntu2
ProcVersionSignature: Ubuntu 3.8.0-17.27-generic 3.8.6
Uname: Linux 3.8.0-17-generic x86_64
ApportVersion: 2.9.2-0ubuntu8
Architecture: amd64
Date: Tue Apr 16 09:52:15 2013
MarkForUpload: True
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: python3.3
UpgradeStatus: Upgraded to raring on 2012-01-31 (440 days ago)