Previously, excessive nesting in expressions would blow the
stack and segfault the interpreter. Now, a hard limit based
on the configured recursion limit and a hardcoded scaling
factor is applied.

Patch by Alessandro Moura.

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.