py4web; return that a server error occured when it is
For the moment, when an internal server error
occur, a modal with text about ssl is open.
This is false and we should show a flash message to say that an error occured.
Maybe use code error 500 to detect it with ajax.
As with py4web migration these types of error can occure more than usual, it can be important to return a correct message to user and that they don't waste time to search about ssl error.