When a user connect to /web/database/manager directly without the
login page before, the request don't have registry.
When the user click to backup a db, a traceback was raised:
return request.registry['ir.http'].content_disposition(filename)
TypeError: 'NoneType' object has no attribute 'getitem'
Because it was impossible to call content_diposable from ir_http
without registry.
Now content disposable has been moved in http.py and is callable from
anywhere.
This commit closes#13192
This commit closes#11583