Patch by Guillaume Pratte.

#12759: sre_parse now raises a proper error when the name of the group is missing.  Initial patch by Serhiy Storchaka.

#16152: fix tokenize to ignore whitespace at the end of the code when no newline is found.  Patch by Ned Batchelder.

  Patch by Alon Horev with update by Alexey Kachayev.

Issue #16284: Prevent keeping unnecessary references to worker functions in concurrent.futures ThreadPoolExecutor.

Thanks to Armin Rigo and Alexey Kachayev.

definition from #15573.