The Flask flash messages are not categorized properly (ref: http://flask.pocoo.org/docs/1.0/patterns/flashing/#flashing-with-categories). Then the default category would be 'message'. Flask AppBuilder would assign CSS class `alert-[category]` to that message when displaying it (ref: https://github.com/dpgaspar/Flask-AppBuilder/blob/master/flask_appbuilder/templates/appbuilder/flash.html ). But 'alert-message' is not specified in bootstrap-theme.css. This makes the the flash messages in the www_rbac UI come with no background color (please check the screenshots attached. We don't see this issue in www UI as all flash messages without categories are classed into 'info').
- Add proper category when we invoke flash().
- We can't use category 'error'. In bootstrap-theme.css, we don't have `alert-error` (we have `alert-danger` instead).
we update bootstrap-theme.css, to add CSS classes 'alert-message' and 'alert-error'. This may help minimize the changes we need to do.