Replace except statement with a PEP-3110 compliant one. This fixes a regression
introduced by c3deeaf714630531d693a6a902b8dabf791858b1
https://bugs.freedesktop.org/show_bug.cgi?id=55690
Reviewed-by: Peter Harris <pharris@opentext.com> Signed-off-by: Uli Schlachter <psychon@znc.in>