Implicit dask import 4164 (#4318)

* Fixed bug involving dask import

* Reformatting using black

* Added line to whats-new.rst

Author: inakleinbottle

doc/whats-new.rst

@@ -37,6 +37,8 @@ New Features
 
 Bug fixes
 ~~~~~~~~~
+- Fixed a bug in backend caused by basic installation of Dask (:issue:`4164`, :pull:`4318`)
+  `Sam Morley <https://github.com/inakleinbottle>`_.
 
 
 Documentation

xarray/backends/locks.py

@@ -72,12 +72,15 @@ def _get_scheduler(get=None, collection=None) -> Optional[str]:
     dask.base.get_scheduler
     """
     try:
-        import dask  # noqa: F401
+        # Fix for bug caused by dask installation that doesn't involve the toolz library
+        # Issue: 4164
+        import dask
+        from dask.base import get_scheduler  # noqa: F401
+
+        actual_get = get_scheduler(get, collection)
     except ImportError:
         return None
 
-    actual_get = dask.base.get_scheduler(get, collection)
-
     try:
         from dask.distributed import Client