def check_existing_filepath(option, opt, value):
    if not exists(value):
        raise OptionValueError(
            (opt, value) % "option %s: file does not exist: %r")
    elif not isfile(value):
        raise OptionValueError(
            "option %s: not a regular file (can't be a directory!): %r" % (opt, value))
    else:
        return value
dataset/ETHPy150Open biocore/pyqi/pyqi/core/interfaces/optparse/__init__.py/check_existing_filepath/swapped operands of `%`