[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.
# copyright %(year)s %(author)s, all rights reserved.# contact %(author-web-site)s -- mailto:%(author-email)s#%(long-license)s"""%(distname)s schema"""