system tests: Fix python crash during tests

As a developer i would like the system tests to not occasionally crash

This seems to be a python crash that takes a while to reporduce. After much testing first fixed a thread leak, but this was not source of problem. Real problem was calling an exception handler function that was a python object that had got garbage collected. We were using an earlier incantation of an exception handler replacement function that we had created, using the upstream one fixed the issue.

Empieza revisando los informes de fallos de las pruebas del sistema y el reemplazo del manejador de excepciones descrito en el issue. Compara el manejador actual con la implementación upstream a la que se hace referencia en el informe y, después, ejecuta las pruebas del sistema repetidamente para comprobar si el fallo intermitente de Python ha desaparecido.

Escrito por el modelo de indexación a partir del texto del issue.