1. The re module contains a table for characters: c1.upper() == c2.upper() and c1 != c2 and c1.lower() == c1 and c2.lower() == c2. For example, 'ς' and 'σ': 'ς'.upper() == 'σ'.upper() == 'Σ'.

   It was generated for 3.5. But newer Python versions support newer Unicode standards, and more such characters were added. For example: 'в' and 'ᲀ': 'в'.upper() == 'ᲀ'.upper() == 'В'.

   Python re lib fails case insensitive matches on Unicode data #56937

2. The code depends on some assumption about characters outside of the BMP range. The comment says that there are only two ranges of cased non-BMP characters, and that RANGE_UNI_IGNORE works with them.

   Now there are more ranges of cased non-BMP characters. Seems the assumption is still true and RANGE_UNI_IGNORE still works, but the comment is outdated.

   IGNORECASE breaks unicode literal range matching #61583

The plan is:

• Regenerate the table with actual Unicode versions for all maintained Python versions.
• Test the assumption and update the comment.
• Add a script and the make target for generating that table with the actual Unicode version (the developed version only).
• For the above assumption, either test it in the script, or make the code working in case it is not true.