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
754413100,MDU6SXNzdWU3NTQ0MTMxMDA=,4634,Read of netCDF file fails with units attribute that is not of type string,5472566,open,0,,,5,2020-12-01T13:52:45Z,2020-12-01T19:29:36Z,,NONE,,,,"When opening a netCDF file which has a variable that has a units attribute with a definition of integer 1, xarray fails to open the file:

```
~/bin/miniconda3/envs/py37_crucial/lib/python3.8/site-packages/xarray/conventions.py in _update_bounds_attributes(variables)
    379     for v in variables.values():
    380         attrs = v.attrs
--> 381         has_date_units = ""units"" in attrs and ""since"" in attrs[""units""]
    382         if has_date_units and ""bounds"" in attrs:
    383             if attrs[""bounds""] in variables:

TypeError: argument of type 'numpy.int64' is not iterable
```

This because line 381 will search for the word ""since"" in an integer type which fails. Of course assigning a integer as units attribute is not wise, but some people tend to assign integer 1 for variables which have no units. 
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