Pandas: pandas.infer_freqとpandas.to_timedeltaの間の非互換性

問題の小さくて完全な例

pd.infer_freqの出力は「D」ですが、 pd.to_timedeltaは「1D」を想定しています。

import pandas as pd
dates = pd.date_range(start='2016-10-01', end='2016-10-10', freq='1D')
freq = pd.infer_freq(dates)
delta = pd.to_timedelta(freq)

期待される出力

delta = Timedelta（ '1 days 00:00:00'）

>>> import pandas as pd
>>> dates = pd.date_range(start='2016-10-01', end='2016-10-10', freq='1D')
>>> dates
DatetimeIndex(['2016-10-01', '2016-10-02', '2016-10-03', '2016-10-04',
               '2016-10-05', '2016-10-06', '2016-10-07', '2016-10-08',
               '2016-10-09', '2016-10-10'],
              dtype='datetime64[ns]', freq='D')
>>> freq = pd.infer_freq(dates)
>>> freq
'D'
>>> delta = pd.to_timedelta(freq)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/iivanov/anaconda2/lib/python2.7/site-packages/pandas/util/decorators.py", line 91, in wrapper
    return func(*args, **kwargs)
  File "/home/iivanov/anaconda2/lib/python2.7/site-packages/pandas/tseries/timedeltas.py", line 102, in to_timedelta
    box=box, errors=errors)
  File "/home/iivanov/anaconda2/lib/python2.7/site-packages/pandas/tseries/timedeltas.py", line 148, in _coerce_scalar_to_timedelta_type
    result = tslib.convert_to_timedelta(r, unit, errors)
  File "pandas/tslib.pyx", line 2941, in pandas.tslib.convert_to_timedelta (pandas/tslib.c:52631)
  File "pandas/tslib.pyx", line 3256, in pandas.tslib.convert_to_timedelta64 (pandas/tslib.c:56028)
  File "pandas/tslib.pyx", line 3188, in pandas.tslib.parse_timedelta_string (pandas/tslib.c:54877)
ValueError: unit abbreviation w/o a number

pd.show_versions()出力