cubicweb #2565882 [testlib] url_publish should behave like a http server [validation pending]

url_publish bypasses the server's error handling, meaning it raises exceptions instead of returning http errors. calling core_handle instead of ctrl.publish would fix this, but needs to also return the request to the caller so it knows what happened.

done in3.17.0
load left0.000
closed by#b399c87df63c [devtools] add http_publish to CubicWebTC (closes #2565882)
patch[devtools] add http_publish to CubicWebTC (closes #2565882) [applied]