merge 3.3 (#16345)

diff --cc Misc/NEWS
index 399bc3fae1d1a3705ad0cde8488a8cef367f02eb,c760a34ae456c249264402372686f220b223070d..909bdffcac20d5976c075c14ca19944e2abe3efb
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -18,9 -15,9 +18,12 @@@ Core and Builtin
  - Fix segfaults on setting __qualname__ on builtin types and attempting to
    delete it on any type.
  
 +- Issue #14625: Rewrite the UTF-32 decoder. It is now 3x to 4x faster. Patch
 +  written by Serhiy Storchaka.
 +
+ - Issue #16345: Fix an infinite loop when ``fromkeys`` on a dict subclass
+   recieved a nonempty dict from the constructor.
+ 
  - Issue #16271: Fix strange bugs that resulted from __qualname__ appearing in a
    class's __dict__ and on type.