It looks like the Python C API has changed so the bundled files created by Cython no longer work with the most recent Python. As a workaround, please install Cython before trying to install `python-qsoptex`. This will cause the files to be recreated properly for the Python version in use.
Hello! I was trying to install python-qsoptex as discussed in the above comment but it was not successful. Do you have any other solution to the problem? Thank you.