python-fitsio: FTBFS on s390x: FAILED fitsio/tests/test_image_compression.py::test_image_compression_gzip_subnormal_cast_to_zero

[Prachi Bhat]

Hi Sebastian, 
I have raised a PR for this issue which has been merged upstream.
https://github.com/esheldon/fitsio/pull/531

Regards
Prachi