--- OptionParser::Arguable#options
    Actual OptionParser object, automatically created if not
    yet.

    If called as iterator, yields with the OptionParser object
    and returns the result of the block. In this case, rescues any
    OptionParser::ParseError exceptions in the block, just emits
    error message to STDERR and returns nil.

    :Parameters:
      : block
        Yielded with the OptionParser instance.

