trying to make a file-URI fails: "client-error-not-possible"

[ekkard gerlach]

I tried to generate a file backend on cups 1.1.18 and 1.1.22. Both with 
CUPS-html-tool. Both failed with:  "client-error-not-possible".

The I generated a CUPS queue by taking somewhat backend, e.g. 
/dev/usblp0. I edited /etc/cups/printers.conf and changed
DeviceURI usb:/dev/usb/lp0  to   DeviceURI file:/tmp/print.prn
and it works! I can cat the print.prn to somewhat printer (e.g. a 
windows machine by using smbclient .... /tmp/print.prn) without fearing 
that cups disables the queue! And without fearing that there are several 
job in a queue so that my customers call me to clean the queue! 
Wonderful!! Hope that helps YOU to make CUPS (and linux) usable!

Why is CUPS-html-config.-tool not able to create file-URI's?

tia
Ekkard