On default, have this single failure on my box (Gentoo amd64):

======================================================================
FAIL: test_sysconfig_module (distutils.tests.test_sysconfig.SysconfigTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/gbr/devel/python/Lib/distutils/tests/test_sysconfig.py", line 105, in test_sysconfig_module
    self.assertEqual(global_sysconfig.get_config_var('LDSHARED'),sysconfig.get_config_var('LDSHARED'))
AssertionError: 'gcc -pthread -shared' != '/usr/bin/clang -shared'
- gcc -pthread -shared
+ /usr/bin/clang -shared


While clang is installed, I haven't set anything to clang while configuring, or in my environment.