When raising an exception, it’s generally a good idea to actually
include the exception value — otherwise Python will re-raise the ‘last
exception which was active in the current scope’, which is not so
useful, especially when you want to print that exception.

Reviewed-by: Sjoerd Simons <sjoerd.simons@collabora.co.uk>
Signed-off-by: Philip Withnall <philip.withnall@collabora.co.uk>
Differential Revision: https://phabricator.apertis.org/D1296