python の pandas_datareader のインポートでエラーが出ます。

###前提・実現したいこと
pythonで pandas_datareaderを使いたいのですがimportでエラーが出ます。原因と解決方を教えてください。よろしくお願いします。

###発生している問題・エラーメッセージ

>>> import pandas_datareader
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Library/Python/2.7/site-packages/pandas_datareader/__init__.py", line 3, in <module>
    from .data import (get_components_yahoo, get_data_famafrench, get_data_google, get_data_yahoo, get_data_enigma,  # noqa
  File "/Library/Python/2.7/site-packages/pandas_datareader/data.py", line 7, in <module>
    from pandas_datareader.google.daily import GoogleDailyReader
  File "/Library/Python/2.7/site-packages/pandas_datareader/google/daily.py", line 1, in <module>
    from pandas_datareader.base import _DailyBaseReader
  File "/Library/Python/2.7/site-packages/pandas_datareader/base.py", line 13, in <module>
    from pandas_datareader._utils import (RemoteDataError, SymbolWarning,
  File "/Library/Python/2.7/site-packages/pandas_datareader/_utils.py", line 4, in <module>
    from pandas_datareader.compat import is_number
  File "/Library/Python/2.7/site-packages/pandas_datareader/compat/__init__.py", line 20, in <module>
    from pandas.util.testing import assert_raises_regex
ImportError: cannot import name assert_raises_regex