issues: 385215500

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id node_id number title user state locked assignee milestone comments created_at updated_at closed_at author_association active_lock_reason draft pull_request body reactions performed_via_github_app state_reason repo type
385215500 MDU6SXNzdWUzODUyMTU1MDA= 2579 sortby(dim) removes dimension from an array if dim is a repeated dimension 14000880 closed 0     1 2018-11-28T11:06:54Z 2018-11-28T22:33:15Z 2018-11-28T22:33:15Z NONE      

Related to #1378. As mentioned there, xarray sometimes seems to have problems with repeated dimensions. sortby() such a dimension seems to be an example:

```python

ds = xr.DataArray(np.eye(2), coords={'alt': [100, 200], 'alt': [100, 200], }, dims=('alt', 'alt'), name='cov').to_dataset()

print(ds) <xarray.Dataset> Dimensions: (alt: 2) Coordinates: * alt (alt) int64 100 200 Data variables: cov (alt, alt) float64 1.0 0.0 0.0 1.0

print(ds.sortby('alt')) <xarray.Dataset> Dimensions: (alt: 2) Coordinates: * alt (alt) int64 100 200 Data variables: cov (alt) float64 1.0 1.0 ```

Output of xr.show_versions()

commit: None python: 2.7.13.final.0 python-bits: 64 OS: Linux OS-release: 4.9.0-8-amd64 machine: x86_64 processor: byteorder: little LC_ALL: None LANG: en_US.UTF-8 LOCALE: en_US.UTF-8 xarray: 0.10.9 pandas: 0.23.4 numpy: 1.15.4 scipy: 1.1.0 netCDF4: 1.2.8 h5netcdf: None h5py: None Nio: None zarr: None cftime: 1.0.0 PseudonetCDF: None rasterio: 0.36.0 iris: None bottleneck: 1.2.1 cyordereddict: 1.0.0 dask: 0.20.2 distributed: None matplotlib: 2.2.3 cartopy: 0.16.0 seaborn: 0.8.1 setuptools: 39.2.0 pip: 18.1 conda: None pytest: 3.8.0 IPython: 5.8.0 sphinx: None 
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   completed 13221727 issue

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