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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def main():
 """Execute main processes."""

    try:
        pkg_version = Update()
        if pkg_version.updatable():
            pkg_version.show_message()
        metadata = control.retreive_metadata()
        parser = parse_options(metadata)
        argvs = sys.argv
        if len(argvs) <= 1:
            parser.print_help()
            sys.exit(1)
        args = parser.parse_args()
        control.print_licences(args, metadata)
        control.check_repository_existence(args)
        control.check_package_existence(args)
        control.generate_package(args)
    except (RuntimeError, BackendFailure, Conflict) as exc:
        sys.stderr.write('{0}\n'.format(exc))
        sys.exit(1)