This commit improves PEP 8 compliance and code robustness by replacing
bare except clauses with specific exception types in Python utility files.

Changes:
- SU2/__init__.py: Use ImportError for optional readline import
- SU2/io/config.py: Use Exception for config file error handling
- SU2/util/ordered_bunch.py: Use Exception and (KeyError, TypeError)
- SU2/util/bunch.py: Use Exception and (KeyError, TypeError)

These changes maintain the original error-handling behavior while making
exception handling more explicit and maintainable. All modified files
pass Python syntax validation.

Signed-off-by: shbhmexe <shubhushukla586@gmail.com>