You may encounter this problem with libselinux and libsemanage when attempting to compile them while Python 3x is set as the default interpreter.

make PYLIBVER=python3.1 pywrap 
make -C src pywrap
make[1]: Entering directory `/var/tmp/portage/sys-libs/libsemanage-2.0.27/work/libsemanage-2.0.27/src'
cc -O2 -march=i686 -pipe -fomit-frame-pointer -mno-tls-direct-seg-refs -fstack-protector-all -I../include -I/usr/include -D_GNU_SOURCE -I/usr/include/python3.1 -fPIC -DSHARED -c -o semanageswig_wrap.lo semanageswig_wrap.c
semanageswig_wrap.c: In function 'PySwigObject_format':
semanageswig_wrap.c:1319: warning: initialization makes pointer from integer without a cast
semanageswig_wrap.c:1321: warning: assignment makes pointer from integer without a cast
semanageswig_wrap.c: In function 'PySwigObject_repr':
semanageswig_wrap.c:1351: warning: initialization makes pointer from integer without a cast
semanageswig_wrap.c: In function 'PySwigObject_print':
semanageswig_wrap.c:1373: warning: passing argument 1 of 'fputs' makes pointer from integer without a cast
/usr/include/stdio.h:662: note: expected 'const char * __restrict__' but argument is of type 'int'
semanageswig_wrap.c: In function 'PySwigObject_str':
semanageswig_wrap.c:1386: warning: return makes pointer from integer without a cast
semanageswig_wrap.c: In function '_PySwigObject_type':
semanageswig_wrap.c:1582: warning: initialization from incompatible pointer type
semanageswig_wrap.c:1583: warning: initialization from incompatible pointer type
semanageswig_wrap.c:1586: warning: initialization from incompatible pointer type
semanageswig_wrap.c:1587: warning: initialization from incompatible pointer type
semanageswig_wrap.c:1594: error: 'coercion' undeclared (first use in this function)
semanageswig_wrap.c:1594: error: (Each undeclared identifier is reported only once
semanageswig_wrap.c:1594: error: for each function it appears in.)
semanageswig_wrap.c:1594: error: expected '}' before numeric constant
semanageswig_wrap.c:1616: warning: initialization makes integer from pointer without a cast
semanageswig_wrap.c:1619: warning: initialization from incompatible pointer type
semanageswig_wrap.c:1620: warning: initialization from incompatible pointer type
semanageswig_wrap.c:1624: warning: initialization from incompatible pointer type
semanageswig_wrap.c:1627: error: 'cmpfunc' undeclared (first use in this function)
semanageswig_wrap.c:1627: error: expected '}' before 'PySwigObject_compare'
semanageswig_wrap.c:1674: error: 'PyTypeObject' has no member named 'ob_type'
semanageswig_wrap.c: In function 'PySwigPacked_repr':
semanageswig_wrap.c:1723: warning: return makes pointer from integer without a cast
semanageswig_wrap.c:1725: warning: return makes pointer from integer without a cast
semanageswig_wrap.c: In function 'PySwigPacked_str':
semanageswig_wrap.c:1734: warning: return makes pointer from integer without a cast
semanageswig_wrap.c:1736: warning: return makes pointer from integer without a cast
semanageswig_wrap.c: In function '_PySwigPacked_type':
semanageswig_wrap.c:1783: warning: initialization makes integer from pointer without a cast
semanageswig_wrap.c:1786: warning: initialization from incompatible pointer type
semanageswig_wrap.c:1787: warning: initialization from incompatible pointer type
semanageswig_wrap.c:1788: warning: initialization from incompatible pointer type
semanageswig_wrap.c:1790: error: 'cmpfunc' undeclared (first use in this function)
semanageswig_wrap.c:1790: error: expected '}' before 'PySwigPacked_compare'
semanageswig_wrap.c:1837: error: 'PyTypeObject' has no member named 'ob_type'
semanageswig_wrap.c: In function '_SWIG_This':
semanageswig_wrap.c:1882: warning: return makes pointer from integer without a cast
semanageswig_wrap.c: In function 'SWIG_Python_GetSwigThis':
semanageswig_wrap.c:1903: warning: assignment makes pointer from integer without a cast
semanageswig_wrap.c: In function 'SWIG_Python_NewShadowInstance':
semanageswig_wrap.c:2117: warning: assignment makes pointer from integer without a cast
semanageswig_wrap.c: In function 'SWIG_Python_SetModule':
semanageswig_wrap.c:2299: warning: initialization makes pointer from integer without a cast
semanageswig_wrap.c: In function 'SWIG_Python_TypeQuery':
semanageswig_wrap.c:2319: warning: initialization makes pointer from integer without a cast
semanageswig_wrap.c: In function 'SWIG_Python_TypeError':
semanageswig_wrap.c:2408: warning: initialization makes pointer from integer without a cast
semanageswig_wrap.c: In function 'SWIG_From_int':
semanageswig_wrap.c:2554: warning: return makes pointer from integer without a cast
semanageswig_wrap.c: In function 'SWIG_FromCharPtrAndSize':
semanageswig_wrap.c:2580: warning: return makes pointer from integer without a cast
semanageswig_wrap.c: In function 'SWIG_AsCharPtrAndSize':
semanageswig_wrap.c:2626: warning: assignment makes pointer from integer without a cast
semanageswig_wrap.c: In function 'swig_varlink_repr':
semanageswig_wrap.c:12117: warning: return makes pointer from integer without a cast
semanageswig_wrap.c: In function 'swig_varlink_str':
semanageswig_wrap.c:12122: warning: initialization makes pointer from integer without a cast
semanageswig_wrap.c: In function 'swig_varlink_print':
semanageswig_wrap.c:12136: warning: format '%s' expects type 'char *', but argument 3 has type 'int'
semanageswig_wrap.c: In function 'swig_varlink_type':
semanageswig_wrap.c:12196: warning: initialization makes integer from pointer without a cast
semanageswig_wrap.c:12199: warning: initialization from incompatible pointer type
semanageswig_wrap.c:12200: warning: initialization from incompatible pointer type
semanageswig_wrap.c:12201: warning: initialization from incompatible pointer type
semanageswig_wrap.c:12204: warning: initialization from incompatible pointer type
semanageswig_wrap.c:12210: warning: initialization from incompatible pointer type
semanageswig_wrap.c:12215: warning: initialization from incompatible pointer type
semanageswig_wrap.c:12231: error: 'PyTypeObject' has no member named 'ob_type'
semanageswig_wrap.c: In function 'init_semanage':
semanageswig_wrap.c:12362: warning: assignment makes pointer from integer without a cast
make[1]: *** [semanageswig_wrap.lo] Error 1
make[1]: Leaving directory `/var/tmp/portage/sys-libs/libsemanage-2.0.27/work/libsemanage-2.0.27/src'
make: *** [pywrap] Error 2
emake failed
 * ERROR: sys-libs/libsemanage-2.0.27 failed (compile phase):
 *   (no error message)
 * 
 * Call stack:
 *     ebuild.sh, line  56:  Called src_compile
 *   environment, line 4388:  Called die
 * The specific snippet of code:
 *       emake PYLIBVER="python$(python_get_version)" pywrap || die
 * 
 * If you need support, post the output of 'emerge --info =sys-libs/libsemanage-2.0.27',
 * the complete build log and the output of 'emerge -pqv =sys-libs/libsemanage-2.0.27'.
 * The complete build log is located at '/var/tmp/portage/sys-libs/libsemanage-2.0.27/temp/build.log'.
 * The ebuild environment file is located at '/var/tmp/portage/sys-libs/libsemanage-2.0.27/temp/environment'.
 * S: '/var/tmp/portage/sys-libs/libsemanage-2.0.27/work/libsemanage-2.0.27'

>>> Failed to emerge sys-libs/libsemanage-2.0.27

To work around:

# eselect python list
Available Python interpreters:
  [1]   python2.6
  [2]   python3.1 *
# eselect python set 1
# emerge libselinux libsemanage

The drawback to this workaround is as soon as you change the default interpreter back to 3.x these packages will be picked up by python-updater.