I installed matplotlib and scikit-bio via conda. An import error listed below occurred when I imported. Appreciate any help to solve it.

Python 2.7.11 |Anaconda 2.4.0 (64-bit)| (default, Dec 6 2015, 18:08:32)
[GCC 4.4.7 20120313 (Red Hat 4.4.7-1)] on linux2
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import skbio
Traceback (most recent call last):
File "", line 1, in
File "/home/fzeng/anaconda/lib/python2.7/site-packages/skbio/init.py", line 14, in
import skbio.io # noqa
File "/home/fzeng/anaconda/lib/python2.7/site-packages/skbio/io/init.py", line 230, in
import_module('skbio.io.format.ordination')
File "/home/fzeng/anaconda/lib/python2.7/importlib/init.py", line 37, in import_module
import(name)
File "/home/fzeng/anaconda/lib/python2.7/site-packages/skbio/io/format/ordination.py", line 195, in
from skbio.stats.ordination import OrdinationResults
File "/home/fzeng/anaconda/lib/python2.7/site-packages/skbio/stats/ordination/init.py", line 115, in
from ._correspondence_analysis import CA
File "/home/fzeng/anaconda/lib/python2.7/site-packages/skbio/stats/ordination/_correspondence_analysis.py", line 13, in
from ._base import Ordination, OrdinationResults
File "/home/fzeng/anaconda/lib/python2.7/site-packages/skbio/stats/ordination/_base.py", line 17, in
from mpl_toolkits.mplot3d import Axes3D
File "/home/fzeng/anaconda/lib/python2.7/site-packages/mpl_toolkits/mplot3d/init.py", line 4, in
from matplotlib.externals import six
ImportError: No module named externals