Better Error Reporting

[Tivoli]

Would be nice to have better error reporting. Right now if there is an error you simply get a generic 500 with "Internal Server Error" as the text. It would be great if there was a body that explained the error like timeout to host or imagemagick errors, etc.

[zzolo]

+1 to this. I am finding it very difficult to figure out why it is not working.

Thanks for the great work!