bounds_error=True ignored in 1D interpolation

[leifdenby]

What happened:

Attempted to interpolate outside coordinate range while passing bounds_error=True through kwargs dictionary (which internally gets passed to scipy.interpolate.interp1d). Instead if interp function raising a ValueError nans are returned.

What you expected to happen:

I expected a ValueError exception to be raised when I've passed in the kwargs bounds_error=True.

Minimal Complete Verifiable Example:

import xarray as xr
import numpy as np

da = xr.DataArray(
    np.sin(0.3 * np.arange(12).reshape(4, 3)),
    [("time", np.arange(4)), ("space", [0.1, 0.2, 0.3])],
)

# this should return nans, as the default is to fill with nans
da.interp(time=3.5)

>   <xarray.DataArray (space: 3)>
>   array([nan, nan, nan])
>   Coordinates:
>     * space    (space) float64 0.1 0.2 0.3
>       time     float64 3.5


# this should raise ValueError, but `bounds_error` is ignored
da.interp(time=3.5, kwargs=dict(bounds_error=True))

>   <xarray.DataArray (space: 3)>
>   array([nan, nan, nan])
>   Coordinates:
>     * space    (space) float64 0.1 0.2 0.3
>       time     float64 3.5

Anything else we need to know?:

I've made a pull-request to fix the issue

Environment:

Output of xr.show_versions()

INSTALLED VERSIONS

commit: None
python: 2.7.15.final.0
python-bits: 64
OS: Linux
OS-release: 3.10.0-957.27.2.el7.x86_64
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: en_GB.UTF-8
LOCALE: None.None

xarray: 0.10.7
pandas: 0.23.0
numpy: 1.14.3
scipy: 1.1.0
netCDF4: None
h5netcdf: None
h5py: 2.7.1
Nio: None
zarr: None
bottleneck: 1.2.1
cyordereddict: None
dask: 0.17.5
distributed: 1.21.8
matplotlib: None
cartopy: None
seaborn: None
setuptools: 39.1.0
pip: 10.0.1
conda: 4.6.4
pytest: 3.5.1
IPython: 5.7.0
sphinx: 1.7.4