Removed raise_from_traceback
ref #29170

This is a pretty old compat function that I think actually hides the errors we are looking for when run via load scheduling. I've converted to a mixture of `raise...from` and `raise (e).with_traceback()` depending on what was available. Not sure it matters too much either way

Let's see...
Looks like this does actually preserve the traceback:

https://travis-ci.org/pandas-dev/pandas/jobs/601566770#L2267 unused sys import Comments addressed and all green here LGTM normally on a deprecation removal we should have the whatsnew note along with all of the changes in the same PR as otherwise it’s harder to track / follow


 Nice to see this removed as a result of our move to `pytest` !