4.0.5 / 4.2.1 : Long card images must have CONTINUE cards after the first card

Description

An error is reported when saving an hdulist to a fits file that only occurs with version 4.2.1 and 4.0.5 of astropy. I’ve tracked the specific patch that is the determining factor to https://github.com/astropy/astropy/pull/11108.

See related issue here https://git.ligo.org/lscsoft/ligo.skymap/-/issues/26

Expected behavior

There should be no output and a fits file should be generated.

Actual behavior

Traceback (most recent call last):
  File "test.py", line 3, in <module>
    data.writeto('test.fits')
  File "/home/ahnitz/projects/env3/lib/python3.8/site-packages/astropy/utils/decorators.py", line 535, in wrapper
    return function(*args, **kwargs)
  File "/home/ahnitz/projects/env3/lib/python3.8/site-packages/astropy/io/fits/hdu/hdulist.py", line 919, in writeto
    self.verify(option=output_verify)
  File "/home/ahnitz/projects/env3/lib/python3.8/site-packages/astropy/io/fits/verify.py", line 73, in verify
    errs = self._verify(opt)
  File "/home/ahnitz/projects/env3/lib/python3.8/site-packages/astropy/io/fits/hdu/hdulist.py", line 1245, in _verify
    result = hdu._verify(option)
  File "/home/ahnitz/projects/env3/lib/python3.8/site-packages/astropy/io/fits/hdu/table.py", line 535, in _verify
    errs = super()._verify(option=option)
  File "/home/ahnitz/projects/env3/lib/python3.8/site-packages/astropy/io/fits/hdu/base.py", line 1587, in _verify
    errs = super()._verify(option=option)
  File "/home/ahnitz/projects/env3/lib/python3.8/site-packages/astropy/io/fits/hdu/base.py", line 1074, in _verify
    errs.append(card._verify(option))
  File "/home/ahnitz/projects/env3/lib/python3.8/site-packages/astropy/io/fits/card.py", line 1118, in _verify
    keyword, valuecomment = self._split()
  File "/home/ahnitz/projects/env3/lib/python3.8/site-packages/astropy/io/fits/card.py", line 815, in _split
    for card in self._itersubcards():
  File "/home/ahnitz/projects/env3/lib/python3.8/site-packages/astropy/io/fits/card.py", line 1170, in _itersubcards
    raise VerifyError(
astropy.io.fits.verify.VerifyError: Long card images must have CONTINUE cards after the first card.

Steps to Reproduce

To reproduce you’ll need the specific data that was trying to be written. I’ve pickled the hdulist to make this possible (file attached and put into save.zip). With that file, one should be able to reproduce with the following.

save.zip

import pickle
data = pickle.load(open('save.pkl', 'rb'))
data.writeto('test.fits')

The data was created by the ligo.skymap library at this line. https://git.ligo.org/lscsoft/ligo.skymap/-/blob/master/ligo/skymap/io/fits.py#L384

System Details

(env3) [ahnitz@hnb697 live]$ python d.py Linux-5.11.8-200.fc33.x86_64-x86_64-with-glibc2.2.5 Python 3.8.8 (default, Feb 20 2021, 00:00:00) [GCC 10.2.1 20201125 (Red Hat 10.2.1-9)] Numpy 1.20.2 astropy 4.2.1 Scipy 1.6.0 Matplotlib 3.4.1

[titodalcanton]

Here is a shorter test case that reproduces the same error for me:

import numpy as np
from astropy.table import Table
from astropy.io import fits


history = ['a.very.loooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong.string']

m = Table(np.ones(16, dtype=float), copy=False)
m.meta.update({'history': history})
hdu = fits.table_to_hdu(m)
hdulist = fits.HDUList([fits.PrimaryHDU(), hdu])
hdulist.writeto('test2.fits', overwrite=True)

[embray]

Workaround in #11487.