Issue #20589: Invoking Path.owner() and Path.group() on Windows now raise

NotImplementedError instead of ImportError.

diff --cc Lib/test/test_pathlib.py
Simple merge

diff --cc Misc/NEWS
index 542af600053efbd75633ca28484ec5df6824935d,3d9a78735cc65bd35683ea9b3ee784cecf460c0d..45d8f2e2b6518d7f4dbc109afe66752c1ab9268c
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -201,16 -90,14 +201,19 @@@ Core and Builtin
  Library
  -------
  
+ - Issue #20589: Invoking Path.owner() and Path.group() on Windows now raise
+   NotImplementedError instead of ImportError.
+ 
  - Issue #26177: Fixed the keys() method for Canvas and Scrollbar widgets.
  
 -- Issue #15068: Got rid of excessive buffering in the fileinput module.
 -  The bufsize parameter is no longer used.
 +- Issue #21042: Make ctypes.util.find_library() return the full path on
 +  Linux, similar to other platforms.  Patch by Tamás Bence Gedai.
 +
 +- Issue #15068: Got rid of excessive buffering in fileinput.
 +  The bufsize parameter is now deprecated and ignored.
 +
 +- Issue #19475: Added an optional argument timespec to the datetime
 +  isoformat() method to choose the precision of the time component.
  
  - Issue #2202: Fix UnboundLocalError in
    AbstractDigestAuthHandler.get_algorithm_impls.  Initial patch by Mathieu Dupuy.