How to use the contextlib2.closing function in contextlib2

"""
    Download a file to a temporary directory, returning it.

    The options provided will control the behaviour of the download algorithm.

      * 'tries' - The maximum number of tries to download the file before
        giving up and raising an exception.
      * 'timeout' - Timeout in seconds before considering the connection to
        have failed.
      * 'verifier' - A function which is called with a filelike object. It
        should return True if the file is okay and appears to be fully
        downloaded.
    """
    logger = logging.getLogger('download')

    with closing(tempfile.NamedTemporaryFile()) as tmp:
        # current file position = number of bytes read
        filepos = 0

        # file size when downloaded, if known
        filesize = None

        # number of attempts so far
        tries = 0

        # last try which resulted in some forward progress (i.e: filepos got
        # bigger)
        last_successful_try = 0

        # maximum number of attempts to make
        max_tries = options.get('tries', 1)

def build(files, srs):
    with closing(tempfile.NamedTemporaryFile(suffix='.vrt')) as vrt:
        # ensure files are actually present before trying to make a VRT from
        # them.
        for f in files:
            assert os.path.exists(f), "Trying to build a VRT including file " \
                "%r, but it does not seem to exist." % f

        args = ["gdalbuildvrt", "-q", "-a_srs", srs, vrt.name ] + files
        status = subprocess.call(args)

        if status != 0:
            raise RuntimeError("Call to gdalbuildvrt failed: status=%r" % status)

        ds = gdal.Open(vrt.name)
        yield ds
        del ds

def download_file(url, filename, session=None, headers=None, **kwargs):
    """Download a file specified.

    :param url: Source URL
    :param filename: Target file on filesystem
    :param session: request session to use
    :param headers: override existing headers in request session
    :return: True on success, False on failure
    """
    try:
        hooks, cookies, verify, proxies = request_defaults(kwargs)

        with closing(session.get(url, allow_redirects=True, stream=True,
                                 verify=verify, headers=headers, cookies=cookies,
                                 hooks=hooks, proxies=proxies)) as resp:

            if not resp.ok:
                logger.debug(u"Requested download url %s returned status code is %s: %s"
                             % (url, resp.status_code, http_code_description(resp.status_code)))
                return False

            try:
                with io.open(filename, 'wb') as fp:
                    for chunk in resp.iter_content(chunk_size=1024):
                        if chunk:
                            fp.write(chunk)
                            fp.flush()

                chmodAsParent(filename)