Bump minimum version requirements for dask from 2.15 to 2.24 (#5726)

* Bump min requirements for dask

* Update whats-new.rst

Author: Illviljan

ci/requirements/py37-min-all-deps.yml

@@ -15,8 +15,8 @@ dependencies:
   - cfgrib=0.9
   - cftime=1.1
   - coveralls
-  - dask=2.15
-  - distributed=2.15
+  - dask=2.24
+  - distributed=2.24
   - h5netcdf=0.8
   - h5py=2.10
   - hdf5=1.10

ci/requirements/py37-min-nep18.yml

@@ -7,8 +7,8 @@ dependencies:
   # require drastically newer packages than everything else
   - python=3.7
   - coveralls
-  - dask=2.9
-  - distributed=2.9
+  - dask=2.24
+  - distributed=2.24
   - numpy=1.17
   - pandas=0.25
   - pint=0.15

doc/whats-new.rst

@@ -35,6 +35,14 @@ New Features
 
 Breaking changes
 ~~~~~~~~~~~~~~~~
+- The minimum versions of some dependencies were changed:
+
+  ============ ====== ====
+  Package      Old    New
+  ============ ====== ====
+  dask         2.15   2.24
+  distributed  2.15   2.24
+  ============ ====== ====
 
 - The ``__repr__`` of a :py:class:`xarray.Dataset`'s ``coords`` and ``data_vars``
   ignore ``xarray.set_option(display_max_rows=...)`` and show the full output

xarray/core/computation.py

@@ -30,7 +30,7 @@
 from .alignment import align, deep_align
 from .merge import merge_attrs, merge_coordinates_without_align
 from .options import OPTIONS, _get_keep_attrs
-from .pycompat import dask_version, is_duck_dask_array
+from .pycompat import is_duck_dask_array
 from .utils import is_dict_like
 from .variable import Variable
 
@@ -715,12 +715,6 @@ def func(*arrays):
                     **dask_gufunc_kwargs,
                 )
 
-                # todo: covers for https://github.com/dask/dask/pull/6207
-                #  remove when minimal dask version >= 2.17.0
-                if dask_version < "2.17.0":
-                    if signature.num_outputs > 1:
-                        res = tuple(res)
-
                 return res
 
         elif dask == "allowed":