issues: 290572700

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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
290572700 MDU6SXNzdWUyOTA1NzI3MDA= 1849 passing unlimited_dims to to_netcdf triggers RuntimeError: NetCDF: Invalid argument 500246 closed 0     12 2018-01-22T18:43:23Z 2019-06-04T20:41:50Z 2019-06-04T20:41:50Z CONTRIBUTOR      

For some datafiles with properties I cannot quite reproduce, .to_netcdf leads to a RuntimeError: NetCDF: Invalid argument if and only if I pass an unlimited_dims corresponding to y. The problem is hard to reproduce. It happens to this particular dataset, but not to seemingly identical ones created from scratch. I attach sample.nc (gzipped so github would let me upload it).

``` $ cat mwe.py

!/usr/bin/env python3.6

import xarray

ds = xarray.open_dataset("sample.nc") ds.to_netcdf("sample2.nc", unlimited_dims=["y"]) $ ncdump sample.nc netcdf sample { dimensions: y = 6 ; variables: float x(y) ; x:_FillValue = NaNf ; int64 y(y) ; data:

x = 0, 0, 0, 0, 0, 0 ;

y = 0, 1, 2, 3, 4, 5 ; } $ ./mwe.py Traceback (most recent call last): File "./mwe.py", line 5, in <module> ds.to_netcdf("sample2.nc", unlimited_dims=["y"]) File "/dev/shm/gerrit/venv/stable-3.6/lib/python3.6/site-packages/xarray/core/dataset.py", line 1133, in to_netcdf unlimited_dims=unlimited_dims) File "/dev/shm/gerrit/venv/stable-3.6/lib/python3.6/site-packages/xarray/backends/api.py", line 627, in to_netcdf unlimited_dims=unlimited_dims) File "/dev/shm/gerrit/venv/stable-3.6/lib/python3.6/site-packages/xarray/core/dataset.py", line 1070, in dump_to_store unlimited_dims=unlimited_dims) File "/dev/shm/gerrit/venv/stable-3.6/lib/python3.6/site-packages/xarray/backends/common.py", line 254, in store args, kwargs) File "/dev/shm/gerrit/venv/stable-3.6/lib/python3.6/site-packages/xarray/backends/common.py", line 221, in store unlimited_dims=unlimited_dims) File "/dev/shm/gerrit/venv/stable-3.6/lib/python3.6/site-packages/xarray/backends/netCDF4_.py", line 339, in set_variables super(NetCDF4DataStore, self).set_variables(args, **kwargs) File "/dev/shm/gerrit/venv/stable-3.6/lib/python3.6/site-packages/xarray/backends/common.py", line 233, in set_variables name, v, check, unlimited_dims=unlimited_dims) File "/dev/shm/gerrit/venv/stable-3.6/lib/python3.6/site-packages/xarray/backends/netCDF4_.py", line 385, in prepare_variable fill_value=fill_value) File "netCDF4/_netCDF4.pyx", line 2437, in netCDF4._netCDF4.Dataset.createVariable File "netCDF4/_netCDF4.pyx", line 3439, in netCDF4._netCDF4.Variable.init File "netCDF4/_netCDF4.pyx", line 1638, in netCDF4._netCDF4._ensure_nc_success RuntimeError: NetCDF: Invalid argument

```

Output of xr.show_versions()

# Paste the output here xr.show_versions() here $ ./mwe.py INSTALLED VERSIONS ------------------ commit: None python: 3.6.1.final.0 python-bits: 64 OS: Linux OS-release: 2.6.32-696.6.3.el6.x86_64 machine: x86_64 processor: x86_64 byteorder: little LC_ALL: None LANG: en_GB.UTF-8 LOCALE: en_GB.UTF-8 xarray: 0.10.0+dev39.ge31cf43 pandas: 0.22.0 numpy: 1.14.0 scipy: 1.0.0 netCDF4: 1.3.1 h5netcdf: None Nio: None zarr: None bottleneck: 1.2.1 cyordereddict: None dask: 0.16.1 distributed: None matplotlib: 2.1.2 cartopy: 0.15.1 seaborn: 0.8.1 setuptools: 38.4.0 pip: 9.0.1 conda: 4.3.16 pytest: 3.1.2 IPython: 6.1.0 sphinx: 1.6.2 [sample.nc.gz](https://github.com/pydata/xarray/files/1653178/sample.nc.gz) 
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   completed 13221727 issue

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