def gzip_opener(path, pattern='', verbose=False):
    """Opener that opens single gzip compressed file.

    :param str path: Path. 
    :param str pattern: Regular expression pattern. 
    :return: Filehandle(s).
    """
    source = path if is_url(path) else os.path.abspath(path)
    filename = os.path.basename(path)

    if pattern and not re.match(pattern, filename):
        logger.verbose('Skipping file: {}, did not match regex pattern "{}"'.format(os.path.abspath(filename), pattern))
        return

    try:
        filehandle = gzip.GzipFile(fileobj=io.BytesIO(urlopen(path).read())) if is_url(path) else gzip.open(path)
        filehandle.read(1)
        filehandle.seek(0)
        logger.verbose('Processing file: {}'.format(source))
        yield filehandle
    except (OSError, IOError):
        raise GZValidationError
Opener that opens single gzip compressed file.

    :param str path: Path. 
    :param str pattern: Regular expression pattern. 
    :return: Filehandle(s).