Issue #14664: It is now possible to use @unittest.skip{If,Unless} on a test class...

diff --cc Lib/unittest/case.py
Simple merge

diff --cc Misc/NEWS
index d6a44e2bc5b333ef03ebd5162679e68464cb615e,2d50fe1c3cde1d03d0c1f04674fdcc84fa7feb3c..d8c91d3312fa58d58ac07e8f74692d6257b50e53
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -71,9 -36,29 +71,12 @@@ Core and Builtin
  Library
  -------
  
+ - Issue #14664: It is now possible to use @unittest.skip{If,Unless} on a
+   test class that doesn't inherit from TestCase (i.e. a mixin).
+ 
 +- Issue #4892: multiprocessing Connections can now be transferred over
 +  multiprocessing Connections.  Patch by Richard Oudkerk (sbt).
 +
  - Issue #14160: TarFile.extractfile() failed to resolve symbolic links when
    the links were not located in an archive subdirectory.