cubicweb #16159863 when using pyramid, we get a NotFound traceback in the UI for 404 error [validation pending]

which logged as well , polluting log files.

priorityimportant
typebug
done in3.24.1
load left0.000
closed by#4e0829ade86f [pyramid] Fix 404 handling
patch[pyramid] Fix 404 handling [applied]