0.15.1 release

[dcherian]

It'd be nice to issue a release by the end of March (two months since previous release)

Please edit this list as you wish.

Must-have

• Raise error when assigning to IndexVariable.values & IndexVariable.data #3862 error when assigning to IndexVariable.values
• Delete associated indexes when deleting coordinate variables. #3840 delete index when deleting coordinate variable
• Re-enable tests xfailed in #3808 and fix new CFTimeIndex failures due to upstream changes #3874 un-xfail the tests from xfail tests due to #3751 #3808 (more upstream-dev cftime failures #3751 (comment))
• html repr fails on non-str Dataset keys #3833, Fix html repr on non-str keys #3870 HTML repr with non-str keys fix (since it is now on by default)

Nice to have

• Add template xarray object kwarg to map_blocks #3816 map_blocks template
• map_blocks: allow user function to add new unindexed dimension. #3817 map_blocks new unindexed dimension
• map_blocks: Allow passing dask-backed objects in args #3818 map_blocks dask args
• provide a error summary for assert_allclose #3847 assert_allclose diff
• Allow ellipsis to be used in stack #3826 ellipsis in stack
• Improve where docstring #3836 where docstring
• some progress on What should pad do about IndexVariables? #3868
• support for units with pint #3594 unit support
• Implement idxmax and idxmin functions #3871 idxmin, idxmax

[mathause]

• un-xfail the tests from xfail tests due to #3751 #3808 (more upstream-dev cftime failures #3751 (comment))
• html repr fails on non-str Dataset keys #3833, PR: Fix html repr on non-str keys #3870

(added to the list above)

[keewis]

if we release without #3594, we need to edit the existing whats-new.rst entry, otherwise we'd claim full support when it currently is partial at most

[max-sixty]

Shall we proceed?

@keewis thoughts re #3594?

[keewis]

we can exclude #3594 (which might justify a new major version?) but then I'd like to edit the entry in whats-new.rst

Edit: see #3878

[max-sixty]

whatsnew fixups in #3879

[keewis]

do we also need to remove Panel from pandas.rst?

[max-sixty]

do we also need to remove Panel from pandas.rst?

Good point, on it now

[max-sixty]

Shall we proceed?

[dcherian]

Ok by me.

[max-sixty]

Done! Will send out tweet & emails now! Thanks everyone!

[dcherian]

wow that was quick! Thanks @max-sixty

[max-sixty]

NB: I screwed up the list of names, there's something about copying from the command line to a Google Groups form; and only visible after sending. I added a note to #3882.

https://groups.google.com/forum/#!topic/xarray/hK158wAviPs

I'll fix before sending to the other lists.