cubicweb #3005547 ConcatFilesHandler doesn't handle errors or concurrency [validation pending]

if ConcatFilesHandler fails to completely write a file it leaves it partially written, which causes painful errors in e.g. ENOSPC conditions.

prioritynormal
typebug
done in3.17.4
load0.250
load left0.000
closed by#7a6ea3468765 [web/views/staticcontrollers] Make ConcatFilesHandler write to a tempfile
patch[web/views/staticcontrollers] Make ConcatFilesHandler write to a tempfile [applied]