Catalog doesn't work with latest pysaml2

[jbrown-xentity]

See https://github.com/GSA/data.gov/issues/3969 for current mitigation, pinning pysaml2 to 7.0.1 We tested this with inventory, and it worked fine: https://github.com/GSA/inventory-app/actions/runs/3153444373

Something is causing specifically catalog to not like this version. It's possible it has something to do with pinning catalog to python 3.7. However, upstream does intend for this to work with python2.7, though the latest main branch test was 3 months ago

How to reproduce

1. Allow normal upgrade of catalog (remove this and update requirements, or change this to latest)
2. Push to development (create local feature branch, and use git push origin feature-branch:develop)
3. Try logging in

Expected behavior

Login works successfully

Actual behavior

Login internal server error

Sketch

Debug via logs, see if there is anything relevant. I expect something is going on with python version since inventory works fine, but there may be other details we're missing.