'Open gzip compressed tar archive name for reading or writing.
Appending is not allowed.'

@classmethod
def gzopen(cls, name, mode='r', fileobj=None, compresslevel=9, **kwargs):

    if (mode not in ('r', 'w')):
        raise ValueError("mode    must    be    'r'    or    'w'")
    try:
        import gzip
        gzip.GzipFile
    except (ImportError, AttributeError):
        raise CompressionError('gzip    module    is    not    available')
    if (fileobj is None):
        fileobj = bltn_open(name, (mode + 'b'))
    try:
        t = cls.taropen(name, mode, gzip.GzipFile(name, mode, compresslevel, fileobj), **kwargs)
    except IOError:
        if (mode == 'r'):
            raise ReadError('not    a    gzip    file')
        raise
    t._extfileobj = False
    return t
