[MacPorts] #60955: `py38-scikit-learn` depends on `threadpoolctl`.

[MacPorts]

#60955: `py38-scikit-learn` depends on `threadpoolctl`.
--------------------+-------------------------------
 Reporter:  iangow  |      Owner:  (none)
     Type:  defect  |     Status:  new
 Priority:  Normal  |  Milestone:
Component:  ports   |    Version:
 Keywords:          |       Port:  py38-scikit-learn
--------------------+-------------------------------
 It seems `py38-scikit-learn` depends on `threadpoolctl`, but this
 dependency isn't coded in.

 ```
 Mac-Pro Downloads % python3
 Python 3.8.5 (default, Jul 21 2020, 18:31:18)
 [Clang 11.0.3 (clang-1103.0.32.62)] on darwin
 Type "help", "copyright", "credits" or "license" for more information.
 >>> from sklearn.cluster import AgglomerativeClustering
 Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
   File
 "/opt/local/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8
 /site-packages/sklearn/cluster/__init__.py", line 6, in <module>
     from ._spectral import spectral_clustering, SpectralClustering
   File
 "/opt/local/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8
 /site-packages/sklearn/cluster/_spectral.py", line 18, in <module>
     from ._kmeans import k_means
   File
 "/opt/local/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8
 /site-packages/sklearn/cluster/_kmeans.py", line 18, in <module>
     from threadpoolctl import threadpool_limits
 ModuleNotFoundError: No module named 'threadpoolctl'
 ```

-- 
Ticket URL: <https://trac.macports.org/ticket/60955>
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