cubicweb #3524182 race condition in ConcatFilesHandler [validation pending]

Sometimes when running tests in parallel I get spurious errors from concat_cached_filepath. I suspect that's due to different processes fighting over the concat tempfile.

priorityminor
typebug
done in3.19.0
load0.250
load left0.000
closed by#7310738fafe5 [web/staticcontrollers] create a unique temporary file for concat handling
patch[web/staticcontrollers] create a unique temporary file for concat handling [applied]