issues: 507468507

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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
507468507 MDU6SXNzdWU1MDc0Njg1MDc= 3401 _get_scheduler() exception if dask.multiprocessing missing 3958036 closed 0     0 2019-10-15T20:35:14Z 2019-10-21T00:17:48Z 2019-10-21T00:17:48Z CONTRIBUTOR      

These lines were recently changed in #3358 https://github.com/pydata/xarray/blob/3f9069ba376afa35c0ca83b09a6126dd24cb8127/xarray/backends/locks.py#L87-L92

If the 'cloudpickle' package is not installed, then dask.multiprocessing is not available. The try/except that used to be wrapped around if actual_get is dask.multiprocessing.get meant that _get_scheduler() worked in that case, returning "threaded" (I assume this was the expected behaviour). After #3358, _get_scheduler() raised an AttributeError: module 'dask' has no attribute 'multiprocessing' until I installed 'cloudpickle'.

Suggest either reverting the changes that removed the try/except or making 'cloudpickle' a dependency.

To reproduce: 1. check 'cloudpickle' is not installed, but 'dask' is 2. execute the following commands ```

import xarray xarray.backends.api._get_scheduler() Expected result: `"threaded"` Actual result:

AttributeError Traceback (most recent call last) <ipython-input-2-20da238796b7> in <module> ----> 1 xarray.backends.api._get_scheduler()

~/.local/lib/python3.6/site-packages/xarray/backends/locks.py in _get_scheduler(get, collection) 87 pass 88 ---> 89 if actual_get is dask.multiprocessing.get: 90 return "multiprocessing" 91 else:

AttributeError: module 'dask' has no attribute 'multiprocessing' ```

 
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