CI: TestSeriesMisc.test_ndarray_compat
https://travis-ci.org/pandas-dev/pandas/jobs/434611709#L2762

Failure on our no-warnings build

```
______________________ TestSeriesMisc.test_ndarray_compat ______________________
[gw0] linux -- Python 3.7.0 /home/travis/miniconda3/envs/pandas/bin/python
self = <pandas.tests.series.test_api.TestSeriesMisc object at 0x7fb7d3ecc080>
    def test_ndarray_compat(self):
    
        # test numpy compat with Series as sub-class of NDFrame
        tsdf = DataFrame(np.random.randn(1000, 3), columns=['A', 'B', 'C'],
                         index=date_range('1/1/2000', periods=1000))
    
        def f(x):
            return x[x.idxmax()]
    
>       result = tsdf.apply(f)
pandas/tests/series/test_api.py:405: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
pandas/core/frame.py:6241: in apply
    return op.get_result()
pandas/core/apply.py:151: in get_result
    return self.apply_standard()
pandas/core/apply.py:245: in apply_standard
    dummy = Series(empty_arr, index=index, dtype=values.dtype)
pandas/core/series.py:277: in __init__
    raise_cast_failure=True)
pandas/core/series.py:4269: in _sanitize_array
    subarr = _try_cast(data, True)
pandas/core/series.py:4227: in _try_cast
    subarr = maybe_cast_to_integer_array(arr, dtype)
pandas/core/dtypes/cast.py:1350: in maybe_cast_to_integer_array
    if np.array_equal(arr, casted):
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
a1 = array([ 6.93813625e-310,  6.93813625e-310,  4.65792425e-310,
        4.65792425e-310,              nan,              n...93813643e-310, -4.77534115e-165,
        6.93813402e-310, -2.05743949e-246,  0.00000000e+000,
        0.00000000e+000])
a2 = array([ 6.93813625e-310,  6.93813625e-310,  4.65792425e-310,
        4.65792425e-310,              nan,              n...93813643e-310, -4.77534115e-165,
        6.93813402e-310, -2.05743949e-246,  0.00000000e+000,
        0.00000000e+000])
    def array_equal(a1, a2):
        """
        True if two arrays have the same shape and elements, False otherwise.
    
        Parameters
        ----------
        a1, a2 : array_like
            Input arrays.
    
        Returns
        -------
        b : bool
            Returns True if the arrays are equal.
    
        See Also
        --------
        allclose: Returns True if two arrays are element-wise equal within a
                  tolerance.
        array_equiv: Returns True if input arrays are shape consistent and all
                     elements equal.
    
        Examples
        --------
        >>> np.array_equal([1, 2], [1, 2])
        True
        >>> np.array_equal(np.array([1, 2]), np.array([1, 2]))
        True
        >>> np.array_equal([1, 2], [1, 2, 3])
        False
        >>> np.array_equal([1, 2], [1, 4])
        False
    
        """
        try:
            a1, a2 = asarray(a1), asarray(a2)
        except Exception:
            return False
        if a1.shape != a2.shape:
            return False
>       return bool(asarray(a1 == a2).all())
E       DeprecationWarning: elementwise comparison failed; this will raise an error in the future.
../../../miniconda3/envs/pandas/lib/python3.7/site-packages/numpy/core/numeric.py:2468: DeprecationWarning

```