fix for 915: account for different use cases of median

[keflavich]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 45.45455% with 6 lines in your changes missing coverage. Please review.

Project coverage is 79.84%. Comparing base (7bc6bac) to head (4d7182f).
Report is 4 commits behind head on master.

❗ Current head 4d7182f differs from pull request most recent head 8486580

Please upload reports for the commit 8486580 to get more accurate results.

Files	Patch %	Lines
spectral_cube/spectral_cube.py	45.45%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #916      +/-   ##
==========================================
- Coverage   79.94%   79.84%   -0.10%     
==========================================
  Files          24       24              
  Lines        6013     6024      +11     
==========================================
+ Hits         4807     4810       +3     
- Misses       1206     1214       +8     

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[keflavich]

There's a bug in warn_slow: it should inspect the function being called to see whether it accepts a how keyword. Presently, it's warning users to use the how keyword even if they're using DaskSpectralCubes

[keflavich]

the last two commits might've been a red herring; I don't think dask is raising the wrong error message.