Issue #11628: cmp_to_key should use __slots__.

diff --cc Lib/functools.py
Simple merge

diff --cc Misc/NEWS
index 76b42b852057269cdc66550751bf55689ff42247,5589daf850e9556169854b2001847d5d88be97ed..b9751b7436bed6cb1fc8004379f1ff0b1051ff71
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -81,9 -49,8 +81,11 @@@ Core and Builtin
  Library
  -------
  
 +- Issue #11371: Mark getopt error messages as localizable.  Patch by Filip
 +  Gruszczyński.
 +
+ - Issue #11628: cmp_to_key generated class should use __slots__
+ 
  - Issue #5537: Fix time2isoz() and time2netscape() functions of
    httplib.cookiejar for expiration year greater than 2038 on 32-bit systems.