Provide way to fix fits file

[bsipocz]

I'm not sure whether this is an imexam or more a ginga issue, possibly both. I'm opening it first here as imexam is the layer the user interacts with:

In [10]: viewer.load_fits('flat.0038.fits')
2019-05-08 18:34:09,643 | E | ginga_viewer.py:633 (load_fits) | Exception loading image: VerifyError("Unparsable card (CD1_1), fix it first with .verify('fix').")
---------------------------------------------------------------------------
VerifyError                               Traceback (most recent call last)
/usr/local/lib/python3.7/site-packages/imexam/ginga_viewer.py in load_fits(self, fname, extver)
    622                     hdu = filedata[extver]
--> 623                     image.load_hdu(hdu)
    624             else:

/usr/local/lib/python3.7/site-packages/ginga/AstroImage.py in load_hdu(self, hdu, fobj, naxispath, inherit_primary_header)
    125         ahdr = self.get_header()
--> 126         self.io.fromHDU(hdu, ahdr)
    127 

/usr/local/lib/python3.7/site-packages/ginga/util/io_fits.py in fromHDU(self, hdu, ahdr)
    107                     continue
--> 108                 ahdr.set_card(card.keyword, card.value, comment=card.comment)
    109         else:

/usr/local/lib/python3.7/site-packages/astropy/io/fits/card.py in value(self)
    284         elif self._valuestring is not None or self._image:
--> 285             value = self._value = self._parse_value()
    286         else:

/usr/local/lib/python3.7/site-packages/astropy/io/fits/card.py in _parse_value(self)
    759             raise VerifyError("Unparsable card ({}), fix it first with "
--> 760                               ".verify('fix').".format(self.keyword))
    761 

VerifyError: Unparsable card (CD1_1), fix it first with .verify('fix').

During handling of the above exception, another exception occurred:

Exception                                 Traceback (most recent call last)
<ipython-input-10-184f17aeac92> in <module>()
----> 1 viewer.load_fits('flat.0038.fits')

/usr/local/lib/python3.7/site-packages/imexam/connect.py in load_fits(self, *args, **kwargs)
    400         else:
    401             self.exam._datafile = args[0]
--> 402         self.window.load_fits(*args, **kwargs)
    403 
    404     def load_region(self, *args, **kwargs):

/usr/local/lib/python3.7/site-packages/imexam/ginga_viewer.py in load_fits(self, fname, extver)
    632         except Exception as e:
    633             self.logger.error("Exception loading image: {0}".format(repr(e)))
--> 634             raise Exception(repr(e))
    635 
    636     def panto_image(self, x, y):

Exception: VerifyError("Unparsable card (CD1_1), fix it first with .verify('fix').")

[sosey]

This looks like an issue with the user FITS file, I'm not too inclined to apply 'fix' for them under the covers, it's probably good they get this error and fix, then resave the file, so that it's valid FITS. FWIW, imexam will also load any numpy array to either ginga or ds9, if you can open the fits file you can display the data array to the viewer with viewer.view(numpy_array_name).

[bsipocz]

I'm not proposing to "fix" it by default, and I could work around this as detailed in #170, but I would find it very useful to have a kwarg that would let me fix it on the fly when opening. Otherwise I agree that it would be nice if all fits files coming down from telescopes would follow the standard, but I'm afraid a world like that would probably is utopia.

[sosey]

okay, I'll add a parameter to the load_fits, but set it to not fix by default. Do you think fix would work as the name?

[bsipocz]

what about verify_fits with None as default, and then the strings as options that can be passed to verify()?