A buildbot produced the following traceback, but the test passed when re-run.  

http://buildbot.python.org/all/builders/x86%20Gentoo%203.3/builds/630/steps/test/logs/stdio

test_loader_deprecated (test.test_pkgutil.ImportlibMigrationTests) ... ok

======================================================================
ERROR: test_iter_importers (test.test_pkgutil.ExtendPathTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "<frozen importlib._bootstrap>", line 1521, in _find_and_load_unlocked
AttributeError: 'module' object has no attribute '__path__'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/var/lib/buildslave/3.3.murray-gentoo/build/Lib/test/test_pkgutil.py", line 206, in test_iter_importers
    importlib.import_module(fullname)
  File "/var/lib/buildslave/3.3.murray-gentoo/build/Lib/importlib/__init__.py", line 90, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1586, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1567, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1524, in _find_and_load_unlocked
ImportError: No module named 'spam.eggs'; spam is not a package

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/var/lib/buildslave/3.3.murray-gentoo/build/Lib/test/test_pkgutil.py", line 226, in test_iter_importers
    del sys.modules['spam.eggs']
KeyError: 'spam.eggs'

This is related to #16163.
Other buildbots failed too, e.g.:
http://buildbot.python.org/all/builders/x86%20RHEL%206%203.3/builds/501
http://buildbot.python.org/all/builders/x86%20Gentoo%20Non-Debug%203.x/builds/4128
http://buildbot.python.org/all/builders/AMD64%20Fedora%20without%20threads%203.3/builds/648

"spam" is a fairly generic name, so I'm guessing something else is leaving a "spam" module around in sys.modules - when I run the tests with the order given in RDM's original report, I get the same error.

I also get a failure in test_builtin though, which is a little weird.

With the attached file, test_builtin fails (so one of the uncommented tests appears to be interfering with that), while test_pkgutil passes (suggesting that the problem there is one the tests flagged with "#TEMP#"

Created #17734 for the weird interference between test_genexps and test_builtin

New changeset 73c79022977b by Nick Coghlan in branch '3.3':
Close #17731: Clean up properly in test_import
http://hg.python.org/cpython/rev/73c79022977b

New changeset 5d4001e32a31 by Nick Coghlan in branch 'default':
Merge fix for #17731 from 3.3
http://hg.python.org/cpython/rev/5d4001e32a31