Backport gzip.decompress for Python 2
Python 2 doesn't have gzip.decompress(data: bytes) -> bytes function.
Backport the two line function from Python 3.6.
Fixes: https://pagure.io/freeipa/issue/7563
Signed-off-by: Christian Heimes <cheimes@redhat.com>
Reviewed-By: Christian Heimes <cheimes@redhat.com>