Local.conf enables multilib like this: 
MACHINE ??= "qemux86-64"
require conf/multilib.conf
MULTILIBS = "multilib:lib64 multilib:lib32"
DEFAULTTUNE_virtclass-multilib-lib64 = "x86-64"
DEFAULTTUNE_virtclass-multilib-lib32 = "x86"

Then bitbake python fails like this:

| /usr/bin/install -c -m 644 ./Lib/plat-linux2/DLFCN.py /usr/lib64/python2.7/plat-linux2
| /usr/bin/install -c -m 644 ./Lib/plat-linux2/IN.py /usr/lib64/python2.7/plat-linux2
| /usr/bin/install -c -m 644 ./Lib/plat-linux2/TYPES.py /usr/lib64/python2.7/plat-linux2
| /usr/bin/install -c ./Lib/plat-linux2/regen /usr/lib64/python2.7/plat-linux2
| /usr/bin/install -c -m 644 ./LICENSE /srv/home/nitin/builds/build-multilib/tmp/work/x86_64-poky-linux/python-2.7.2-r0.5/image/usr/lib64/python2.7/LICENSE.txt
| PYTHONPATH=/srv/home/nitin/builds/build-multilib/tmp/work/x86_64-poky-linux/python-2.7.2-r0.5/image/usr/lib64/python2.7  LD_LIBRARY_PATH=/srv/home/nitin/builds/build-multilib/tmp/work/x86_64-poky-linux/python-2.7.2-r0.5/Python-2.7.2:/srv/home/nitin/builds/build-multilib/tmp/sysroots/x86_64-linux/usr/bin/../lib/pseudo/lib:/srv/home/nitin/builds/build-multilib/tmp/sysroots/x86_64-linux/usr/bin/../lib/pseudo/lib64 \
| 	/srv/home/nitin/builds/build-multilib/tmp/sysroots/x86_64-linux/usr/bin/python -Wi -tt /srv/home/nitin/builds/build-multilib/tmp/work/x86_64-poky-linux/python-2.7.2-r0.5/image/usr/lib64/python2.7/compileall.py \
| 	-d /usr/lib64/python2.7 -f \
| 	-x 'bad_coding|badsyntax|site-packages|lib2to3/tests/data' \
| 	/srv/home/nitin/builds/build-multilib/tmp/work/x86_64-poky-linux/python-2.7.2-r0.5/image/usr/lib64/python2.7
| Traceback (most recent call last):
|   File "/srv/home/nitin/builds/build-multilib/tmp/work/x86_64-poky-linux/python-2.7.2-r0.5/image/usr/lib64/python2.7/site.py", line 569, in <module>
|     main()
|   File "/srv/home/nitin/builds/build-multilib/tmp/work/x86_64-poky-linux/python-2.7.2-r0.5/image/usr/lib64/python2.7/site.py", line 551, in main
|     known_paths = addusersitepackages(known_paths)
|   File "/srv/home/nitin/builds/build-multilib/tmp/work/x86_64-poky-linux/python-2.7.2-r0.5/image/usr/lib64/python2.7/site.py", line 278, in addusersitepackages
|     user_site = getusersitepackages()
|   File "/srv/home/nitin/builds/build-multilib/tmp/work/x86_64-poky-linux/python-2.7.2-r0.5/image/usr/lib64/python2.7/site.py", line 253, in getusersitepackages
|     user_base = getuserbase() # this will also set USER_BASE
|   File "/srv/home/nitin/builds/build-multilib/tmp/work/x86_64-poky-linux/python-2.7.2-r0.5/image/usr/lib64/python2.7/site.py", line 243, in getuserbase
|     USER_BASE = get_config_var('userbase')
|   File "/srv/home/nitin/builds/build-multilib/tmp/work/x86_64-poky-linux/python-2.7.2-r0.5/image/usr/lib64/python2.7/sysconfig.py", line 520, in get_config_var
|     return get_config_vars().get(name)
|   File "/srv/home/nitin/builds/build-multilib/tmp/work/x86_64-poky-linux/python-2.7.2-r0.5/image/usr/lib64/python2.7/sysconfig.py", line 419, in get_config_vars
|     _init_posix(_CONFIG_VARS)
|   File "/srv/home/nitin/builds/build-multilib/tmp/work/x86_64-poky-linux/python-2.7.2-r0.5/image/usr/lib64/python2.7/sysconfig.py", line 287, in _init_posix
|     raise IOError(msg)
| IOError: invalid Python installation: unable to open /usr/lib/python2.7/config/Makefile (No such file or directory)
| make: *** [libinstall] Error 1
| ERROR: oe_runmake failed
NOTE: package python-2.7.2-r0.5: task do_install: Failed
ERROR: Task 2 (/srv/home/nitin/prj/poky.git/meta/recipes-devtools/python/python_2.7.2.bb, do_install) failed with exit code '1'
NOTE: Tasks Summary: Attempted 816 tasks of which 801 didn't need to be rerun and 1 failed.

Summary: 1 task failed:
  /srv/home/nitin/prj/poky.git/meta/recipes-devtools/python/python_2.7.2.bb, do_install
Summary: There was 1 ERROR message shown, returning a non-zero exit code.


As Yu Ke has worked on the python multilib patch, Assigning this bug to him.