#8 CFITSIO crash on YX imaging

[André Offringa]

When imaging YX with cleaning, version 1.2.1 crashes when it tries to restore the files, because YX is also being tried to restore. The crash looks like:

Writing residual image... DONE
Writing model image... DONE
Loading wsclean-residual-YX-tmp.fits
terminate called after throwing an instance of 'std::runtime_error'
what(): CFITSIO reported error when performing IO on file 'wsclean-residual-YX-tmp.fits': could not open the named file (failed to find or open the following file: (ffopen)wsclean-residual-YX-tmp.fits)
Aborted (core dumped)

(Independently reported by both G. Foster and G. Bernardi)

[André Offringa]

It turns out that this was mainly a problem in the text of the error message: since 1.2, YX images can not be cleaned without specifying -joinpolarizations. This is a feature, as it doesn't make much sense to clean YX without including the imaginary values and joining with the other polarizations. Hence, -joinpolarizations is required.

In version 1.3, it is explicitly tested whether imaging YX without -joinpolarizations is performed, and if this is the case, an error message describing this is displayed. I assume this fixes this issue.