suggestion: improved error message compared to "not authorized"

[RichardNeill]

I just spent a very long time tracking down the source of the error message in my web application:
convert: not authorized `upload.pdf' @ error/constitute.c/ReadImage/412.
This is because I assumed "not authorized" meant something to do with file permissions, directory permissions, apache's systemd private /tmp, etc.
This assumption is, I think, entirely reasonable... but it turns out to be wrong: it's a policy.xml issue (because ImageMagic has now upgraded to a version that doesn't do PDFs by default).

Please could you make this error message a bit more explicit, so that users who see it are pointed in the right direction? I propose:
"convert: format not authorized by policy.xml `upload.pdf' @ error/constitute.c/ReadImage/412."
This way, I'd get the hint that this is something unexpected that is to do with imagemagick's configuration.

Another thing that is confusing is that the full error message reads:
convert: not authorized `upload.pdf' @ error/constitute.c/ReadImage/412.
convert: no images defined `output.jpg' @ error/convert.c/ConvertImageCommand/3258.
I think after the first error, convert should quit: the 2nd errormessage is actually a bit misleading.

Thanks.

[magick]

Thanks for the problem report. We can reproduce it and will have a patch to fix it in GIT master branch @ https://github.com/ImageMagick/ImageMagick later today. The patch will be available in the beta releases of ImageMagick @ https://www.imagemagick.org/download/beta/ by sometime tomorrow.