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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 package_existent(name):
 """Search package. * :class:`bootstrap_py.exceptions.Conflict` exception occurs when user specified name has already existed. * :class:`bootstrap_py.exceptions.BackendFailure` exception occurs when PyPI service is down. :param str name: package name """

    try:
        response = requests.get(PYPI_URL.format(name))
        if response.ok:
            msg = ('[error] "{0}" is registered already in PyPI.\n'
                   '\tSpecify another package name.').format(name)
            raise Conflict(msg)
    except (socket.gaierror,
            Timeout,
            ConnectionError,
            HTTPError) as exc:
        raise BackendFailure(exc)