[polly] polly: Fix three Python files that contain SyntaxErrors (PR #124424)

[Michael Kruse via llvm-commits]

Meinersbur wrote:

Thanks for the PR.  These are python2 source, and only syntax errors in Python3. 

threshold.py has been updated at https://github.com/creachadair/imath/commit/03fc6627b94aaea8c512a31f86c824b166bf2fa7. Changes in this repository will be overwritten the next time `update-isl.py`. It will pick the revision from https://repo.or.cz/isl.git/history/HEAD:/imath. To update that, contact the maintainer at isl-development at googlegroups.com. The script is not used within Polly, hence I would rather not make changes here.

The other two need to complete update Python3. Did you actually execute these scripts to confirm they work with Python3.

https://github.com/llvm/llvm-project/pull/124424