Fragile try/except logic in MIS

[blnicho]

This issue stems from a comment in PR #3403 posted by @jsiirola in #3403 (review)

The MIS implementation uses a bare (catch-all) "except:" clause when guarding against non-zero solver return codes. This could suppress any number of errors and there would be no way to know what was going on. It would be good to revisit this and see if the bare "except:" can be removed.

    try:
        results = solver.solve(modified_model, tee=tee)
    except:
        results = None

Code from this file: https://github.com/bknueven/pyomo/blob/57f5e06d9549b58099f98b35072f35ded3f50419/pyomo/contrib/iis/mis.py#L285-L288