Issue #25554: Got rid of circular references in regular expression parsing.

diff --cc Misc/NEWS
index 77d05abc7af05c3d901f9faea68ad5ae8778cf4c,f2ce94afe691e7a14b47b444de0298f2cfecac43..26ca26ba0cb4657e7eb7f58debe949bf45d61d64
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -72,9 -54,8 +72,11 @@@ Core and Builtin
  Library
  -------
  
+ - Issue #25554: Got rid of circular references in regular expression parsing.
+ 
 +- Issue #18973: Command-line interface of the calendar module now uses argparse
 +  instead of optparse.
 +
  - Issue #25510: fileinput.FileInput.readline() now returns b'' instead of ''
    at the end if the FileInput was opened with binary mode.
    Patch by Ryosuke Ito.