Supress tracebacks for "expected" exceptions in more places
    
    afbee03f26 tried to suppress tracebacks, but I was testing it by calling
    'PYTHONPATH=… python -m rust2rpm' and completely missed the fact that the
    setuptools entrypoint wrapper calls main() directly and is not covered by
    this.
    
    Also, the same should be done for cargo-inspector.