[web/views/staticcontrollers] Make ConcatFilesHandler write to a tempfile In order to be more resistant to errors such as ENOSPC, and against different threads accessing the same static data, we: - concatenate data files to a temporary file, and rename it once we're done - delete the tempfile in case of errors - protect the creation of the cache_concat file with a lock Closes #3005547

#!/usr/bin/env python
from cubicweb.cwctl import run
import sys
run(sys.argv[1:])