[web server] #1642893 issue a 403 instead of a 500 on Unauthorized exception To do so, we allow an arbitrary code to be passed to ``error_handler``. Default error code is still 500.

from os.path import join
from cubicweb.toolsutils import create_dir

option_renamed('pyro-application-id', 'pyro-instance-id')

create_dir(join(config.appdatahome, 'backup'))