[web] return 403 for Unauthorized, not 401
401 is reserved to HTTP authentication. Just because it's also called
"unauthorized" doesn't mean it's the same as cubicweb's Unauthorized
exception. Closes #3648809.
\.svn
^build$
^dist$
\.pyc$
\.pyo$
\.bak$
\.old$
\~$
\#.*?\#$
\.swp$
^doc/book/en/apidoc$
\.old$
syntax: regexp
.*/data/database/.*\.sqlite
.*/data/database/.*\.config
.*/data/database/tmpdb.*
.*/data/ldapdb/.*
^doc/html/
^doc/doctrees/
^doc/book/en/devweb/js_api/
data/pgdb/