Doc build failing on master

[TomAugspurger]

Seems like https://travis-ci.org/pandas-dev/pandas/jobs/370527551 was the first one that failed.

Exception occurred:
  File "/tmp/doc/sphinxext/numpydoc/docscrape.py", line 375, in _error_location
    raise ValueError(msg)
ValueError: The section Returns appears twice in the docstring of None in None.

[TomAugspurger]

In [7]: print(pd.core.window.Rolling.quantile.__doc__)

rolling quantile

Parameters
----------
quantile : float
    0 <= quantile <= 1
interpolation : {'linear', 'lower', 'higher', 'midpoint', 'nearest'}
    .. versionadded:: 0.23.0

    This optional parameter specifies the interpolation method to use,
    when the desired quantile lies between two data points `i` and `j`:

        * linear: `i + (j - i) * fraction`, where `fraction` is the
          fractional part of the index surrounded by `i` and `j`.
        * lower: `i`.
        * higher: `j`.
        * nearest: `i` or `j` whichever is nearest.
        * midpoint: (`i` + `j`) / 2.

Returns
-------
Series or DataFrame
    Returned object type is determined by the caller of the rolling
    calculation.

Examples
--------
>>> s = Series([1, 2, 3, 4])
>>> s.rolling(2).quantile(.4, interpolation='lower')
0    NaN
1    1.0
2    2.0
3    3.0
dtype: float64

>>> s.rolling(2).quantile(.4, interpolation='midpoint')
0    NaN
1    1.5
2    2.5
3    3.5
dtype: float64

See Also
--------
pandas.Series.quantile : Computes value at the given quantile over all data
    in Series.
pandas.DataFrame.quantile : Computes values at the given quantile over
    requested axis in DataFrame.



Returns
-------
same type as input

See also
--------
pandas.Series.rolling
pandas.DataFrame.rolling

#20497